<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/arch/arm64/kernel/fpsimd.c, branch v6.13</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux</title>
<updated>2024-11-19T02:10:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-11-19T02:10:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=ba1f9c8fe3d443a78814cdf8ac8f9829b5ca7095'/>
<id>ba1f9c8fe3d443a78814cdf8ac8f9829b5ca7095</id>
<content type='text'>
Pull arm64 updates from Catalin Marinas:

 - Support for running Linux in a protected VM under the Arm
   Confidential Compute Architecture (CCA)

 - Guarded Control Stack user-space support. Current patches follow the
   x86 ABI of implicitly creating a shadow stack on clone(). Subsequent
   patches (already on the list) will add support for clone3() allowing
   finer-grained control of the shadow stack size and placement from
   libc

 - AT_HWCAP3 support (not running out of HWCAP2 bits yet but we are
   getting close with the upcoming dpISA support)

 - Other arch features:

     - In-kernel use of the memcpy instructions, FEAT_MOPS (previously
       only exposed to user; uaccess support not merged yet)

     - MTE: hugetlbfs support and the corresponding kselftests

     - Optimise CRC32 using the PMULL instructions

     - Support for FEAT_HAFT enabling ARCH_HAS_NONLEAF_PMD_YOUNG

     - Optimise the kernel TLB flushing to use the range operations

     - POE/pkey (permission overlays): further cleanups after bringing
       the signal handler in line with the x86 behaviour for 6.12

 - arm64 perf updates:

     - Support for the NXP i.MX91 PMU in the existing IMX driver

     - Support for Ampere SoCs in the Designware PCIe PMU driver

     - Support for Marvell's 'PEM' PCIe PMU present in the 'Odyssey' SoC

     - Support for Samsung's 'Mongoose' CPU PMU

     - Support for PMUv3.9 finer-grained userspace counter access
       control

     - Switch back to platform_driver::remove() now that it returns
       'void'

     - Add some missing events for the CXL PMU driver

 - Miscellaneous arm64 fixes/cleanups:

     - Page table accessors cleanup: type updates, drop unused macros,
       reorganise arch_make_huge_pte() and clean up pte_mkcont(), sanity
       check addresses before runtime P4D/PUD folding

     - Command line override for ID_AA64MMFR0_EL1.ECV (advertising the
       FEAT_ECV for the generic timers) allowing Linux to boot with
       firmware deployments that don't set SCTLR_EL3.ECVEn

     - ACPI/arm64: tighten the check for the array of platform timer
       structures and adjust the error handling procedure in
       gtdt_parse_timer_block()

     - Optimise the cache flush for the uprobes xol slot (skip if no
       change) and other uprobes/kprobes cleanups

     - Fix the context switching of tpidrro_el0 when kpti is enabled

     - Dynamic shadow call stack fixes

     - Sysreg updates

     - Various arm64 kselftest improvements

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (168 commits)
  arm64: tls: Fix context-switching of tpidrro_el0 when kpti is enabled
  kselftest/arm64: Try harder to generate different keys during PAC tests
  kselftest/arm64: Don't leak pipe fds in pac.exec_sign_all()
  arm64/ptrace: Clarify documentation of VL configuration via ptrace
  kselftest/arm64: Corrupt P0 in the irritator when testing SSVE
  acpi/arm64: remove unnecessary cast
  arm64/mm: Change protval as 'pteval_t' in map_range()
  kselftest/arm64: Fix missing printf() argument in gcs/gcs-stress.c
  kselftest/arm64: Add FPMR coverage to fp-ptrace
  kselftest/arm64: Expand the set of ZA writes fp-ptrace does
  kselftets/arm64: Use flag bits for features in fp-ptrace assembler code
  kselftest/arm64: Enable build of PAC tests with LLVM=1
  kselftest/arm64: Check that SVCR is 0 in signal handlers
  selftests/mm: Fix unused function warning for aarch64_write_signal_pkey()
  kselftest/arm64: Fix printf() compiler warnings in the arm64 syscall-abi.c tests
  kselftest/arm64: Fix printf() warning in the arm64 MTE prctl() test
  kselftest/arm64: Fix printf() compiler warnings in the arm64 fp tests
  kselftest/arm64: Fix build with stricter assemblers
  arm64/scs: Drop unused prototype __pi_scs_patch_vmlinux()
  arm64/scs: Deal with 64-bit relative offsets in FDE frames
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull arm64 updates from Catalin Marinas:

 - Support for running Linux in a protected VM under the Arm
   Confidential Compute Architecture (CCA)

 - Guarded Control Stack user-space support. Current patches follow the
   x86 ABI of implicitly creating a shadow stack on clone(). Subsequent
   patches (already on the list) will add support for clone3() allowing
   finer-grained control of the shadow stack size and placement from
   libc

 - AT_HWCAP3 support (not running out of HWCAP2 bits yet but we are
   getting close with the upcoming dpISA support)

 - Other arch features:

     - In-kernel use of the memcpy instructions, FEAT_MOPS (previously
       only exposed to user; uaccess support not merged yet)

     - MTE: hugetlbfs support and the corresponding kselftests

     - Optimise CRC32 using the PMULL instructions

     - Support for FEAT_HAFT enabling ARCH_HAS_NONLEAF_PMD_YOUNG

     - Optimise the kernel TLB flushing to use the range operations

     - POE/pkey (permission overlays): further cleanups after bringing
       the signal handler in line with the x86 behaviour for 6.12

 - arm64 perf updates:

     - Support for the NXP i.MX91 PMU in the existing IMX driver

     - Support for Ampere SoCs in the Designware PCIe PMU driver

     - Support for Marvell's 'PEM' PCIe PMU present in the 'Odyssey' SoC

     - Support for Samsung's 'Mongoose' CPU PMU

     - Support for PMUv3.9 finer-grained userspace counter access
       control

     - Switch back to platform_driver::remove() now that it returns
       'void'

     - Add some missing events for the CXL PMU driver

 - Miscellaneous arm64 fixes/cleanups:

     - Page table accessors cleanup: type updates, drop unused macros,
       reorganise arch_make_huge_pte() and clean up pte_mkcont(), sanity
       check addresses before runtime P4D/PUD folding

     - Command line override for ID_AA64MMFR0_EL1.ECV (advertising the
       FEAT_ECV for the generic timers) allowing Linux to boot with
       firmware deployments that don't set SCTLR_EL3.ECVEn

     - ACPI/arm64: tighten the check for the array of platform timer
       structures and adjust the error handling procedure in
       gtdt_parse_timer_block()

     - Optimise the cache flush for the uprobes xol slot (skip if no
       change) and other uprobes/kprobes cleanups

     - Fix the context switching of tpidrro_el0 when kpti is enabled

     - Dynamic shadow call stack fixes

     - Sysreg updates

     - Various arm64 kselftest improvements

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (168 commits)
  arm64: tls: Fix context-switching of tpidrro_el0 when kpti is enabled
  kselftest/arm64: Try harder to generate different keys during PAC tests
  kselftest/arm64: Don't leak pipe fds in pac.exec_sign_all()
  arm64/ptrace: Clarify documentation of VL configuration via ptrace
  kselftest/arm64: Corrupt P0 in the irritator when testing SSVE
  acpi/arm64: remove unnecessary cast
  arm64/mm: Change protval as 'pteval_t' in map_range()
  kselftest/arm64: Fix missing printf() argument in gcs/gcs-stress.c
  kselftest/arm64: Add FPMR coverage to fp-ptrace
  kselftest/arm64: Expand the set of ZA writes fp-ptrace does
  kselftets/arm64: Use flag bits for features in fp-ptrace assembler code
  kselftest/arm64: Enable build of PAC tests with LLVM=1
  kselftest/arm64: Check that SVCR is 0 in signal handlers
  selftests/mm: Fix unused function warning for aarch64_write_signal_pkey()
  kselftest/arm64: Fix printf() compiler warnings in the arm64 syscall-abi.c tests
  kselftest/arm64: Fix printf() warning in the arm64 MTE prctl() test
  kselftest/arm64: Fix printf() compiler warnings in the arm64 fp tests
  kselftest/arm64: Fix build with stricter assemblers
  arm64/scs: Drop unused prototype __pi_scs_patch_vmlinux()
  arm64/scs: Deal with 64-bit relative offsets in FDE frames
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>arm64/sve: Discard stale CPU state when handling SVE traps</title>
<updated>2024-11-06T13:49:39+00:00</updated>
<author>
<name>Mark Brown</name>
<email>broonie@kernel.org</email>
</author>
<published>2024-10-30T20:23:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=751ecf6afd6568adc98f2a6052315552c0483d18'/>
<id>751ecf6afd6568adc98f2a6052315552c0483d18</id>
<content type='text'>
The logic for handling SVE traps manipulates saved FPSIMD/SVE state
incorrectly, and a race with preemption can result in a task having
TIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state
is stale (e.g. with SVE traps enabled). This has been observed to result
in warnings from do_sve_acc() where SVE traps are not expected while
TIF_SVE is set:

|         if (test_and_set_thread_flag(TIF_SVE))
|                 WARN_ON(1); /* SVE access shouldn't have trapped */

Warnings of this form have been reported intermittently, e.g.

  https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgqpdBj+QwDLeSg=JhGg@mail.gmail.com/
  https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@google.com/

The race can occur when the SVE trap handler is preempted before and
after manipulating the saved FPSIMD/SVE state, starting and ending on
the same CPU, e.g.

| void do_sve_acc(unsigned long esr, struct pt_regs *regs)
| {
|         // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled
|         // task-&gt;fpsimd_cpu is 0.
|         // per_cpu_ptr(&amp;fpsimd_last_state, 0) is task.
|
|         ...
|
|         // Preempted; migrated from CPU 0 to CPU 1.
|         // TIF_FOREIGN_FPSTATE is set.
|
|         get_cpu_fpsimd_context();
|
|         if (test_and_set_thread_flag(TIF_SVE))
|                 WARN_ON(1); /* SVE access shouldn't have trapped */
|
|         sve_init_regs() {
|                 if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
|                         ...
|                 } else {
|                         fpsimd_to_sve(current);
|                         current-&gt;thread.fp_type = FP_STATE_SVE;
|                 }
|         }
|
|         put_cpu_fpsimd_context();
|
|         // Preempted; migrated from CPU 1 to CPU 0.
|         // task-&gt;fpsimd_cpu is still 0
|         // If per_cpu_ptr(&amp;fpsimd_last_state, 0) is still task then:
|         // - Stale HW state is reused (with SVE traps enabled)
|         // - TIF_FOREIGN_FPSTATE is cleared
|         // - A return to userspace skips HW state restore
| }

Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set
by calling fpsimd_flush_task_state() to detach from the saved CPU
state. This ensures that a subsequent context switch will not reuse the
stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the
new state to be reloaded from memory prior to a return to userspace.

Fixes: cccb78ce89c4 ("arm64/sve: Rework SVE access trap to convert state in registers")
Reported-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
Cc: stable@vger.kernel.org
Reviewed-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Link: https://lore.kernel.org/r/20241030-arm64-fpsimd-foreign-flush-v1-1-bd7bd66905a2@kernel.org
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The logic for handling SVE traps manipulates saved FPSIMD/SVE state
incorrectly, and a race with preemption can result in a task having
TIF_SVE set and TIF_FOREIGN_FPSTATE clear even though the live CPU state
is stale (e.g. with SVE traps enabled). This has been observed to result
in warnings from do_sve_acc() where SVE traps are not expected while
TIF_SVE is set:

|         if (test_and_set_thread_flag(TIF_SVE))
|                 WARN_ON(1); /* SVE access shouldn't have trapped */

Warnings of this form have been reported intermittently, e.g.

  https://lore.kernel.org/linux-arm-kernel/CA+G9fYtEGe_DhY2Ms7+L7NKsLYUomGsgqpdBj+QwDLeSg=JhGg@mail.gmail.com/
  https://lore.kernel.org/linux-arm-kernel/000000000000511e9a060ce5a45c@google.com/

The race can occur when the SVE trap handler is preempted before and
after manipulating the saved FPSIMD/SVE state, starting and ending on
the same CPU, e.g.

| void do_sve_acc(unsigned long esr, struct pt_regs *regs)
| {
|         // Trap on CPU 0 with TIF_SVE clear, SVE traps enabled
|         // task-&gt;fpsimd_cpu is 0.
|         // per_cpu_ptr(&amp;fpsimd_last_state, 0) is task.
|
|         ...
|
|         // Preempted; migrated from CPU 0 to CPU 1.
|         // TIF_FOREIGN_FPSTATE is set.
|
|         get_cpu_fpsimd_context();
|
|         if (test_and_set_thread_flag(TIF_SVE))
|                 WARN_ON(1); /* SVE access shouldn't have trapped */
|
|         sve_init_regs() {
|                 if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
|                         ...
|                 } else {
|                         fpsimd_to_sve(current);
|                         current-&gt;thread.fp_type = FP_STATE_SVE;
|                 }
|         }
|
|         put_cpu_fpsimd_context();
|
|         // Preempted; migrated from CPU 1 to CPU 0.
|         // task-&gt;fpsimd_cpu is still 0
|         // If per_cpu_ptr(&amp;fpsimd_last_state, 0) is still task then:
|         // - Stale HW state is reused (with SVE traps enabled)
|         // - TIF_FOREIGN_FPSTATE is cleared
|         // - A return to userspace skips HW state restore
| }

Fix the case where the state is not live and TIF_FOREIGN_FPSTATE is set
by calling fpsimd_flush_task_state() to detach from the saved CPU
state. This ensures that a subsequent context switch will not reuse the
stale CPU state, and will instead set TIF_FOREIGN_FPSTATE, forcing the
new state to be reloaded from memory prior to a return to userspace.

Fixes: cccb78ce89c4 ("arm64/sve: Rework SVE access trap to convert state in registers")
Reported-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
Cc: stable@vger.kernel.org
Reviewed-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Link: https://lore.kernel.org/r/20241030-arm64-fpsimd-foreign-flush-v1-1-bd7bd66905a2@kernel.org
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>arm64/fpsimd: Fix a typo</title>
<updated>2024-11-04T12:48:24+00:00</updated>
<author>
<name>Christophe JAILLET</name>
<email>christophe.jaillet@wanadoo.fr</email>
</author>
<published>2024-11-02T09:31:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=525fd6a1b34ea8ce42e12db38380eed0efefb5d5'/>
<id>525fd6a1b34ea8ce42e12db38380eed0efefb5d5</id>
<content type='text'>
s/FPSMID/FPSIMD/
M and I swapped. Fix it.

Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Link: https://lore.kernel.org/r/2cbcb42615e9265bccc9b746465d7998382e605d.1730539907.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
s/FPSMID/FPSIMD/
M and I swapped. Fix it.

Signed-off-by: Christophe JAILLET &lt;christophe.jaillet@wanadoo.fr&gt;
Link: https://lore.kernel.org/r/2cbcb42615e9265bccc9b746465d7998382e605d.1730539907.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sysctl: treewide: constify the ctl_table argument of proc_handlers</title>
<updated>2024-07-24T18:59:29+00:00</updated>
<author>
<name>Joel Granados</name>
<email>j.granados@samsung.com</email>
</author>
<published>2024-07-24T18:59:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=78eb4ea25cd5fdbdae7eb9fdf87b99195ff67508'/>
<id>78eb4ea25cd5fdbdae7eb9fdf87b99195ff67508</id>
<content type='text'>
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh &lt;linux@weissschuh.net&gt;
Signed-off-by: Thomas Weißschuh &lt;linux@weissschuh.net&gt;
Co-developed-by: Joel Granados &lt;j.granados@samsung.com&gt;
Signed-off-by: Joel Granados &lt;j.granados@samsung.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh &lt;linux@weissschuh.net&gt;
Signed-off-by: Thomas Weißschuh &lt;linux@weissschuh.net&gt;
Co-developed-by: Joel Granados &lt;j.granados@samsung.com&gt;
Signed-off-by: Joel Granados &lt;j.granados@samsung.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>arm64/fpsimd: Avoid erroneous elide of user state reload</title>
<updated>2024-05-22T11:46:39+00:00</updated>
<author>
<name>Ard Biesheuvel</name>
<email>ardb@kernel.org</email>
</author>
<published>2024-05-22T09:13:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=e92bee9f861b466c676f0200be3e46af7bc4ac6b'/>
<id>e92bee9f861b466c676f0200be3e46af7bc4ac6b</id>
<content type='text'>
TIF_FOREIGN_FPSTATE is a 'convenience' flag that should reflect whether
the current CPU holds the most recent user mode FP/SIMD state of the
current task. It combines two conditions:
- whether the current CPU's FP/SIMD state belongs to the task;
- whether that state is the most recent associated with the task (as a
  task may have executed on other CPUs as well).

When a task is scheduled in and TIF_KERNEL_FPSTATE is set, it means the
task was in a kernel mode NEON section when it was scheduled out, and so
the kernel mode FP/SIMD state is restored. Since this implies that the
current CPU is *not* holding the most recent user mode FP/SIMD state of
the current task, the TIF_FOREIGN_FPSTATE flag is set too, so that the
user mode FP/SIMD state is reloaded from memory when returning to
userland.

However, the task may be scheduled out after completing the kernel mode
NEON section, but before returning to userland. When this happens, the
TIF_FOREIGN_FPSTATE flag will not be preserved, but will be set as usual
the next time the task is scheduled in, and will be based on the above
conditions.

This means that, rather than setting TIF_FOREIGN_FPSTATE when scheduling
in a task with TIF_KERNEL_FPSTATE set, the underlying state should be
updated so that TIF_FOREIGN_FPSTATE will assume the expected value as a
result.

So instead, call fpsimd_flush_cpu_state(), which takes care of this.

Closes: https://lore.kernel.org/all/cb8822182231850108fa43e0446a4c7f@kernel.org
Reported-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Fixes: aefbab8e77eb ("arm64: fpsimd: Preserve/restore kernel mode NEON at context switch")
Cc: Mark Brown &lt;broonie@kernel.org&gt;
Cc: Dave Martin &lt;Dave.Martin@arm.com&gt;
Cc: Janne Grunau &lt;j@jannau.net&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Ard Biesheuvel &lt;ardb@kernel.org&gt;
Tested-by: Janne Grunau &lt;j@jannau.net&gt;
Tested-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Reviewed-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20240522091335.335346-2-ardb+git@google.com
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
TIF_FOREIGN_FPSTATE is a 'convenience' flag that should reflect whether
the current CPU holds the most recent user mode FP/SIMD state of the
current task. It combines two conditions:
- whether the current CPU's FP/SIMD state belongs to the task;
- whether that state is the most recent associated with the task (as a
  task may have executed on other CPUs as well).

When a task is scheduled in and TIF_KERNEL_FPSTATE is set, it means the
task was in a kernel mode NEON section when it was scheduled out, and so
the kernel mode FP/SIMD state is restored. Since this implies that the
current CPU is *not* holding the most recent user mode FP/SIMD state of
the current task, the TIF_FOREIGN_FPSTATE flag is set too, so that the
user mode FP/SIMD state is reloaded from memory when returning to
userland.

However, the task may be scheduled out after completing the kernel mode
NEON section, but before returning to userland. When this happens, the
TIF_FOREIGN_FPSTATE flag will not be preserved, but will be set as usual
the next time the task is scheduled in, and will be based on the above
conditions.

This means that, rather than setting TIF_FOREIGN_FPSTATE when scheduling
in a task with TIF_KERNEL_FPSTATE set, the underlying state should be
updated so that TIF_FOREIGN_FPSTATE will assume the expected value as a
result.

So instead, call fpsimd_flush_cpu_state(), which takes care of this.

Closes: https://lore.kernel.org/all/cb8822182231850108fa43e0446a4c7f@kernel.org
Reported-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Fixes: aefbab8e77eb ("arm64: fpsimd: Preserve/restore kernel mode NEON at context switch")
Cc: Mark Brown &lt;broonie@kernel.org&gt;
Cc: Dave Martin &lt;Dave.Martin@arm.com&gt;
Cc: Janne Grunau &lt;j@jannau.net&gt;
Cc: stable@vger.kernel.org
Signed-off-by: Ard Biesheuvel &lt;ardb@kernel.org&gt;
Tested-by: Janne Grunau &lt;j@jannau.net&gt;
Tested-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Reviewed-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20240522091335.335346-2-ardb+git@google.com
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Reapply "arm64: fpsimd: Implement lazy restore for kernel mode FPSIMD"</title>
<updated>2024-05-22T10:55:00+00:00</updated>
<author>
<name>Will Deacon</name>
<email>will@kernel.org</email>
</author>
<published>2024-05-22T10:53:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f481bb32d60e45fb3d19ea68ce79c5629f3fc3a0'/>
<id>f481bb32d60e45fb3d19ea68ce79c5629f3fc3a0</id>
<content type='text'>
This reverts commit b8995a18417088bb53f87c49d200ec72a9dd4ec1.

Ard managed to reproduce the dm-crypt corruption problem and got to the
bottom of it, so re-apply the problematic patch in preparation for
fixing things properly.

Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reverts commit b8995a18417088bb53f87c49d200ec72a9dd4ec1.

Ard managed to reproduce the dm-crypt corruption problem and got to the
bottom of it, so re-apply the problematic patch in preparation for
fixing things properly.

Cc: stable@vger.kernel.org
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Revert "arm64: fpsimd: Implement lazy restore for kernel mode FPSIMD"</title>
<updated>2024-05-17T11:55:55+00:00</updated>
<author>
<name>Will Deacon</name>
<email>will@kernel.org</email>
</author>
<published>2024-05-17T11:55:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=b8995a18417088bb53f87c49d200ec72a9dd4ec1'/>
<id>b8995a18417088bb53f87c49d200ec72a9dd4ec1</id>
<content type='text'>
This reverts commit 2632e25217696712681dd1f3ecc0d71624ea3b23.

Johannes (and others) report data corruption with dm-crypt on Apple M1
which has been bisected to this change. Revert the offending commit
while we figure out what's going on.

Cc: stable@vger.kernel.org
Reported-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Link: https://lore.kernel.org/all/D1B7GPIR9K1E.5JFV37G0YTIF@shadowice.org/
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reverts commit 2632e25217696712681dd1f3ecc0d71624ea3b23.

Johannes (and others) report data corruption with dm-crypt on Apple M1
which has been bisected to this change. Revert the offending commit
while we figure out what's going on.

Cc: stable@vger.kernel.org
Reported-by: Johannes Nixdorf &lt;mixi@shadowice.org&gt;
Link: https://lore.kernel.org/all/D1B7GPIR9K1E.5JFV37G0YTIF@shadowice.org/
Signed-off-by: Will Deacon &lt;will@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux</title>
<updated>2024-03-14T22:35:42+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-03-14T22:35:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=6d75c6f40a03c97e1ecd683ae54e249abb9d922b'/>
<id>6d75c6f40a03c97e1ecd683ae54e249abb9d922b</id>
<content type='text'>
Pull arm64 updates from Catalin Marinas:
 "The major features are support for LPA2 (52-bit VA/PA with 4K and 16K
  pages), the dpISA extension and Rust enabled on arm64. The changes are
  mostly contained within the usual arch/arm64/, drivers/perf, the arm64
  Documentation and kselftests. The exception is the Rust support which
  touches some generic build files.

  Summary:

   - Reorganise the arm64 kernel VA space and add support for LPA2 (at
     stage 1, KVM stage 2 was merged earlier) - 52-bit VA/PA address
     range with 4KB and 16KB pages

   - Enable Rust on arm64

   - Support for the 2023 dpISA extensions (data processing ISA), host
     only

   - arm64 perf updates:

      - StarFive's StarLink (integrates one or more CPU cores with a
        shared L3 memory system) PMU support

      - Enable HiSilicon Erratum 162700402 quirk for HIP09

      - Several updates for the HiSilicon PCIe PMU driver

      - Arm CoreSight PMU support

      - Convert all drivers under drivers/perf/ to use .remove_new()

   - Miscellaneous:

      - Don't enable workarounds for "rare" errata by default

      - Clean up the DAIF flags handling for EL0 returns (in preparation
        for NMI support)

      - Kselftest update for ptrace()

      - Update some of the sysreg field definitions

      - Slight improvement in the code generation for inline asm I/O
        accessors to permit offset addressing

      - kretprobes: acquire regs via a BRK exception (previously done
        via a trampoline handler)

      - SVE/SME cleanups, comment updates

      - Allow CALL_OPS+CC_OPTIMIZE_FOR_SIZE with clang (previously
        disabled due to gcc silently ignoring -falign-functions=N)"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (134 commits)
  Revert "mm: add arch hook to validate mmap() prot flags"
  Revert "arm64: mm: add support for WXN memory translation attribute"
  Revert "ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512"
  ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
  kselftest/arm64: Add 2023 DPISA hwcap test coverage
  kselftest/arm64: Add basic FPMR test
  kselftest/arm64: Handle FPMR context in generic signal frame parser
  arm64/hwcap: Define hwcaps for 2023 DPISA features
  arm64/ptrace: Expose FPMR via ptrace
  arm64/signal: Add FPMR signal handling
  arm64/fpsimd: Support FEAT_FPMR
  arm64/fpsimd: Enable host kernel access to FPMR
  arm64/cpufeature: Hook new identification registers up to cpufeature
  docs: perf: Fix build warning of hisi-pcie-pmu.rst
  perf: starfive: Only allow COMPILE_TEST for 64-bit architectures
  MAINTAINERS: Add entry for StarFive StarLink PMU
  docs: perf: Add description for StarFive's StarLink PMU
  dt-bindings: perf: starfive: Add JH8100 StarLink PMU
  perf: starfive: Add StarLink PMU support
  docs: perf: Update usage for target filter of hisi-pcie-pmu
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull arm64 updates from Catalin Marinas:
 "The major features are support for LPA2 (52-bit VA/PA with 4K and 16K
  pages), the dpISA extension and Rust enabled on arm64. The changes are
  mostly contained within the usual arch/arm64/, drivers/perf, the arm64
  Documentation and kselftests. The exception is the Rust support which
  touches some generic build files.

  Summary:

   - Reorganise the arm64 kernel VA space and add support for LPA2 (at
     stage 1, KVM stage 2 was merged earlier) - 52-bit VA/PA address
     range with 4KB and 16KB pages

   - Enable Rust on arm64

   - Support for the 2023 dpISA extensions (data processing ISA), host
     only

   - arm64 perf updates:

      - StarFive's StarLink (integrates one or more CPU cores with a
        shared L3 memory system) PMU support

      - Enable HiSilicon Erratum 162700402 quirk for HIP09

      - Several updates for the HiSilicon PCIe PMU driver

      - Arm CoreSight PMU support

      - Convert all drivers under drivers/perf/ to use .remove_new()

   - Miscellaneous:

      - Don't enable workarounds for "rare" errata by default

      - Clean up the DAIF flags handling for EL0 returns (in preparation
        for NMI support)

      - Kselftest update for ptrace()

      - Update some of the sysreg field definitions

      - Slight improvement in the code generation for inline asm I/O
        accessors to permit offset addressing

      - kretprobes: acquire regs via a BRK exception (previously done
        via a trampoline handler)

      - SVE/SME cleanups, comment updates

      - Allow CALL_OPS+CC_OPTIMIZE_FOR_SIZE with clang (previously
        disabled due to gcc silently ignoring -falign-functions=N)"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (134 commits)
  Revert "mm: add arch hook to validate mmap() prot flags"
  Revert "arm64: mm: add support for WXN memory translation attribute"
  Revert "ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512"
  ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
  kselftest/arm64: Add 2023 DPISA hwcap test coverage
  kselftest/arm64: Add basic FPMR test
  kselftest/arm64: Handle FPMR context in generic signal frame parser
  arm64/hwcap: Define hwcaps for 2023 DPISA features
  arm64/ptrace: Expose FPMR via ptrace
  arm64/signal: Add FPMR signal handling
  arm64/fpsimd: Support FEAT_FPMR
  arm64/fpsimd: Enable host kernel access to FPMR
  arm64/cpufeature: Hook new identification registers up to cpufeature
  docs: perf: Fix build warning of hisi-pcie-pmu.rst
  perf: starfive: Only allow COMPILE_TEST for 64-bit architectures
  MAINTAINERS: Add entry for StarFive StarLink PMU
  docs: perf: Add description for StarFive's StarLink PMU
  dt-bindings: perf: starfive: Add JH8100 StarLink PMU
  perf: starfive: Add StarLink PMU support
  docs: perf: Update usage for target filter of hisi-pcie-pmu
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branches 'for-next/reorg-va-space', 'for-next/rust-for-arm64', 'for-next/misc', 'for-next/daif-cleanup', 'for-next/kselftest', 'for-next/documentation', 'for-next/sysreg' and 'for-next/dpisa', remote-tracking branch 'arm64/for-next/perf' into for-next/core</title>
<updated>2024-03-07T19:04:55+00:00</updated>
<author>
<name>Catalin Marinas</name>
<email>catalin.marinas@arm.com</email>
</author>
<published>2024-03-07T19:04:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0c5ade742e91d7bf3a508bf6223deb7410009b6d'/>
<id>0c5ade742e91d7bf3a508bf6223deb7410009b6d</id>
<content type='text'>
* arm64/for-next/perf: (39 commits)
  docs: perf: Fix build warning of hisi-pcie-pmu.rst
  perf: starfive: Only allow COMPILE_TEST for 64-bit architectures
  MAINTAINERS: Add entry for StarFive StarLink PMU
  docs: perf: Add description for StarFive's StarLink PMU
  dt-bindings: perf: starfive: Add JH8100 StarLink PMU
  perf: starfive: Add StarLink PMU support
  docs: perf: Update usage for target filter of hisi-pcie-pmu
  drivers/perf: hisi_pcie: Merge find_related_event() and get_event_idx()
  drivers/perf: hisi_pcie: Relax the check on related events
  drivers/perf: hisi_pcie: Check the target filter properly
  drivers/perf: hisi_pcie: Add more events for counting TLP bandwidth
  drivers/perf: hisi_pcie: Fix incorrect counting under metric mode
  drivers/perf: hisi_pcie: Introduce hisi_pcie_pmu_get_event_ctrl_val()
  drivers/perf: hisi_pcie: Rename hisi_pcie_pmu_{config,clear}_filter()
  drivers/perf: hisi: Enable HiSilicon Erratum 162700402 quirk for HIP09
  perf/arm_cspmu: Add devicetree support
  dt-bindings/perf: Add Arm CoreSight PMU
  perf/arm_cspmu: Simplify counter reset
  perf/arm_cspmu: Simplify attribute groups
  perf/arm_cspmu: Simplify initialisation
  ...

* for-next/reorg-va-space:
  : Reorganise the arm64 kernel VA space in preparation for LPA2 support
  : (52-bit VA/PA).
  arm64: kaslr: Adjust randomization range dynamically
  arm64: mm: Reclaim unused vmemmap region for vmalloc use
  arm64: vmemmap: Avoid base2 order of struct page size to dimension region
  arm64: ptdump: Discover start of vmemmap region at runtime
  arm64: ptdump: Allow all region boundaries to be defined at boot time
  arm64: mm: Move fixmap region above vmemmap region
  arm64: mm: Move PCI I/O emulation region above the vmemmap region

* for-next/rust-for-arm64:
  : Enable Rust support for arm64
  arm64: rust: Enable Rust support for AArch64
  rust: Refactor the build target to allow the use of builtin targets

* for-next/misc:
  : Miscellaneous arm64 patches
  ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
  arm64: Remove enable_daif macro
  arm64/hw_breakpoint: Directly use ESR_ELx_WNR for an watchpoint exception
  arm64: cpufeatures: Clean up temporary variable to simplify code
  arm64: Update setup_arch() comment on interrupt masking
  arm64: remove unnecessary ifdefs around is_compat_task()
  arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang
  arm64/sme: Ensure that all fields in SMCR_EL1 are set to known values
  arm64/sve: Ensure that all fields in ZCR_EL1 are set to known values
  arm64/sve: Document that __SVE_VQ_MAX is much larger than needed
  arm64: make member of struct pt_regs and it's offset macro in the same order
  arm64: remove unneeded BUILD_BUG_ON assertion
  arm64: kretprobes: acquire the regs via a BRK exception
  arm64: io: permit offset addressing
  arm64: errata: Don't enable workarounds for "rare" errata by default

* for-next/daif-cleanup:
  : Clean up DAIF handling for EL0 returns
  arm64: Unmask Debug + SError in do_notify_resume()
  arm64: Move do_notify_resume() to entry-common.c
  arm64: Simplify do_notify_resume() DAIF masking

* for-next/kselftest:
  : Miscellaneous arm64 kselftest patches
  kselftest/arm64: Test that ptrace takes effect in the target process

* for-next/documentation:
  : arm64 documentation patches
  arm64/sme: Remove spurious 'is' in SME documentation
  arm64/fp: Clarify effect of setting an unsupported system VL
  arm64/sme: Fix cut'n'paste in ABI document
  arm64/sve: Remove bitrotted comment about syscall behaviour

* for-next/sysreg:
  : sysreg updates
  arm64/sysreg: Update ID_AA64DFR0_EL1 register
  arm64/sysreg: Update ID_DFR0_EL1 register fields
  arm64/sysreg: Add register fields for ID_AA64DFR1_EL1

* for-next/dpisa:
  : Support for 2023 dpISA extensions
  kselftest/arm64: Add 2023 DPISA hwcap test coverage
  kselftest/arm64: Add basic FPMR test
  kselftest/arm64: Handle FPMR context in generic signal frame parser
  arm64/hwcap: Define hwcaps for 2023 DPISA features
  arm64/ptrace: Expose FPMR via ptrace
  arm64/signal: Add FPMR signal handling
  arm64/fpsimd: Support FEAT_FPMR
  arm64/fpsimd: Enable host kernel access to FPMR
  arm64/cpufeature: Hook new identification registers up to cpufeature
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
* arm64/for-next/perf: (39 commits)
  docs: perf: Fix build warning of hisi-pcie-pmu.rst
  perf: starfive: Only allow COMPILE_TEST for 64-bit architectures
  MAINTAINERS: Add entry for StarFive StarLink PMU
  docs: perf: Add description for StarFive's StarLink PMU
  dt-bindings: perf: starfive: Add JH8100 StarLink PMU
  perf: starfive: Add StarLink PMU support
  docs: perf: Update usage for target filter of hisi-pcie-pmu
  drivers/perf: hisi_pcie: Merge find_related_event() and get_event_idx()
  drivers/perf: hisi_pcie: Relax the check on related events
  drivers/perf: hisi_pcie: Check the target filter properly
  drivers/perf: hisi_pcie: Add more events for counting TLP bandwidth
  drivers/perf: hisi_pcie: Fix incorrect counting under metric mode
  drivers/perf: hisi_pcie: Introduce hisi_pcie_pmu_get_event_ctrl_val()
  drivers/perf: hisi_pcie: Rename hisi_pcie_pmu_{config,clear}_filter()
  drivers/perf: hisi: Enable HiSilicon Erratum 162700402 quirk for HIP09
  perf/arm_cspmu: Add devicetree support
  dt-bindings/perf: Add Arm CoreSight PMU
  perf/arm_cspmu: Simplify counter reset
  perf/arm_cspmu: Simplify attribute groups
  perf/arm_cspmu: Simplify initialisation
  ...

* for-next/reorg-va-space:
  : Reorganise the arm64 kernel VA space in preparation for LPA2 support
  : (52-bit VA/PA).
  arm64: kaslr: Adjust randomization range dynamically
  arm64: mm: Reclaim unused vmemmap region for vmalloc use
  arm64: vmemmap: Avoid base2 order of struct page size to dimension region
  arm64: ptdump: Discover start of vmemmap region at runtime
  arm64: ptdump: Allow all region boundaries to be defined at boot time
  arm64: mm: Move fixmap region above vmemmap region
  arm64: mm: Move PCI I/O emulation region above the vmemmap region

* for-next/rust-for-arm64:
  : Enable Rust support for arm64
  arm64: rust: Enable Rust support for AArch64
  rust: Refactor the build target to allow the use of builtin targets

* for-next/misc:
  : Miscellaneous arm64 patches
  ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512
  arm64: Remove enable_daif macro
  arm64/hw_breakpoint: Directly use ESR_ELx_WNR for an watchpoint exception
  arm64: cpufeatures: Clean up temporary variable to simplify code
  arm64: Update setup_arch() comment on interrupt masking
  arm64: remove unnecessary ifdefs around is_compat_task()
  arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang
  arm64/sme: Ensure that all fields in SMCR_EL1 are set to known values
  arm64/sve: Ensure that all fields in ZCR_EL1 are set to known values
  arm64/sve: Document that __SVE_VQ_MAX is much larger than needed
  arm64: make member of struct pt_regs and it's offset macro in the same order
  arm64: remove unneeded BUILD_BUG_ON assertion
  arm64: kretprobes: acquire the regs via a BRK exception
  arm64: io: permit offset addressing
  arm64: errata: Don't enable workarounds for "rare" errata by default

* for-next/daif-cleanup:
  : Clean up DAIF handling for EL0 returns
  arm64: Unmask Debug + SError in do_notify_resume()
  arm64: Move do_notify_resume() to entry-common.c
  arm64: Simplify do_notify_resume() DAIF masking

* for-next/kselftest:
  : Miscellaneous arm64 kselftest patches
  kselftest/arm64: Test that ptrace takes effect in the target process

* for-next/documentation:
  : arm64 documentation patches
  arm64/sme: Remove spurious 'is' in SME documentation
  arm64/fp: Clarify effect of setting an unsupported system VL
  arm64/sme: Fix cut'n'paste in ABI document
  arm64/sve: Remove bitrotted comment about syscall behaviour

* for-next/sysreg:
  : sysreg updates
  arm64/sysreg: Update ID_AA64DFR0_EL1 register
  arm64/sysreg: Update ID_DFR0_EL1 register fields
  arm64/sysreg: Add register fields for ID_AA64DFR1_EL1

* for-next/dpisa:
  : Support for 2023 dpISA extensions
  kselftest/arm64: Add 2023 DPISA hwcap test coverage
  kselftest/arm64: Add basic FPMR test
  kselftest/arm64: Handle FPMR context in generic signal frame parser
  arm64/hwcap: Define hwcaps for 2023 DPISA features
  arm64/ptrace: Expose FPMR via ptrace
  arm64/signal: Add FPMR signal handling
  arm64/fpsimd: Support FEAT_FPMR
  arm64/fpsimd: Enable host kernel access to FPMR
  arm64/cpufeature: Hook new identification registers up to cpufeature
</pre>
</div>
</content>
</entry>
<entry>
<title>arm64/fpsimd: Support FEAT_FPMR</title>
<updated>2024-03-07T17:14:53+00:00</updated>
<author>
<name>Mark Brown</name>
<email>broonie@kernel.org</email>
</author>
<published>2024-03-06T23:14:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=203f2b95a882dc46dd9873562167db69a1f61711'/>
<id>203f2b95a882dc46dd9873562167db69a1f61711</id>
<content type='text'>
FEAT_FPMR defines a new EL0 accessible register FPMR use to configure the
FP8 related features added to the architecture at the same time. Detect
support for this register and context switch it for EL0 when present.

Due to the sharing of responsibility for saving floating point state
between the host kernel and KVM FP8 support is not yet implemented in KVM
and a stub similar to that used for SVCR is provided for FPMR in order to
avoid bisection issues. To make it easier to share host state with the
hypervisor we store FPMR as a hardened usercopy field in uw (along with
some padding).

Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20240306-arm64-2023-dpisa-v5-3-c568edc8ed7f@kernel.org
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
FEAT_FPMR defines a new EL0 accessible register FPMR use to configure the
FP8 related features added to the architecture at the same time. Detect
support for this register and context switch it for EL0 when present.

Due to the sharing of responsibility for saving floating point state
between the host kernel and KVM FP8 support is not yet implemented in KVM
and a stub similar to that used for SVCR is provided for FPMR in order to
avoid bisection issues. To make it easier to share host state with the
hypervisor we store FPMR as a hardened usercopy field in uw (along with
some padding).

Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
Link: https://lore.kernel.org/r/20240306-arm64-2023-dpisa-v5-3-c568edc8ed7f@kernel.org
Signed-off-by: Catalin Marinas &lt;catalin.marinas@arm.com&gt;
</pre>
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