<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/arch/x86/include/uapi/asm, branch v6.8</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm</title>
<updated>2024-01-17T21:03:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-01-17T21:03:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=09d1c6a80f2cf94c6e70be919203473d4ab8e26c'/>
<id>09d1c6a80f2cf94c6e70be919203473d4ab8e26c</id>
<content type='text'>
Pull kvm updates from Paolo Bonzini:
 "Generic:

   - Use memdup_array_user() to harden against overflow.

   - Unconditionally advertise KVM_CAP_DEVICE_CTRL for all
     architectures.

   - Clean up Kconfigs that all KVM architectures were selecting

   - New functionality around "guest_memfd", a new userspace API that
     creates an anonymous file and returns a file descriptor that refers
     to it. guest_memfd files are bound to their owning virtual machine,
     cannot be mapped, read, or written by userspace, and cannot be
     resized. guest_memfd files do however support PUNCH_HOLE, which can
     be used to switch a memory area between guest_memfd and regular
     anonymous memory.

   - New ioctl KVM_SET_MEMORY_ATTRIBUTES allowing userspace to specify
     per-page attributes for a given page of guest memory; right now the
     only attribute is whether the guest expects to access memory via
     guest_memfd or not, which in Confidential SVMs backed by SEV-SNP,
     TDX or ARM64 pKVM is checked by firmware or hypervisor that
     guarantees confidentiality (AMD PSP, Intel TDX module, or EL2 in
     the case of pKVM).

  x86:

   - Support for "software-protected VMs" that can use the new
     guest_memfd and page attributes infrastructure. This is mostly
     useful for testing, since there is no pKVM-like infrastructure to
     provide a meaningfully reduced TCB.

   - Fix a relatively benign off-by-one error when splitting huge pages
     during CLEAR_DIRTY_LOG.

   - Fix a bug where KVM could incorrectly test-and-clear dirty bits in
     non-leaf TDP MMU SPTEs if a racing thread replaces a huge SPTE with
     a non-huge SPTE.

   - Use more generic lockdep assertions in paths that don't actually
     care about whether the caller is a reader or a writer.

   - let Xen guests opt out of having PV clock reported as "based on a
     stable TSC", because some of them don't expect the "TSC stable" bit
     (added to the pvclock ABI by KVM, but never set by Xen) to be set.

   - Revert a bogus, made-up nested SVM consistency check for
     TLB_CONTROL.

   - Advertise flush-by-ASID support for nSVM unconditionally, as KVM
     always flushes on nested transitions, i.e. always satisfies flush
     requests. This allows running bleeding edge versions of VMware
     Workstation on top of KVM.

   - Sanity check that the CPU supports flush-by-ASID when enabling SEV
     support.

   - On AMD machines with vNMI, always rely on hardware instead of
     intercepting IRET in some cases to detect unmasking of NMIs

   - Support for virtualizing Linear Address Masking (LAM)

   - Fix a variety of vPMU bugs where KVM fail to stop/reset counters
     and other state prior to refreshing the vPMU model.

   - Fix a double-overflow PMU bug by tracking emulated counter events
     using a dedicated field instead of snapshotting the "previous"
     counter. If the hardware PMC count triggers overflow that is
     recognized in the same VM-Exit that KVM manually bumps an event
     count, KVM would pend PMIs for both the hardware-triggered overflow
     and for KVM-triggered overflow.

   - Turn off KVM_WERROR by default for all configs so that it's not
     inadvertantly enabled by non-KVM developers, which can be
     problematic for subsystems that require no regressions for W=1
     builds.

   - Advertise all of the host-supported CPUID bits that enumerate
     IA32_SPEC_CTRL "features".

   - Don't force a masterclock update when a vCPU synchronizes to the
     current TSC generation, as updating the masterclock can cause
     kvmclock's time to "jump" unexpectedly, e.g. when userspace
     hotplugs a pre-created vCPU.

   - Use RIP-relative address to read kvm_rebooting in the VM-Enter
     fault paths, partly as a super minor optimization, but mostly to
     make KVM play nice with position independent executable builds.

   - Guard KVM-on-HyperV's range-based TLB flush hooks with an #ifdef on
     CONFIG_HYPERV as a minor optimization, and to self-document the
     code.

   - Add CONFIG_KVM_HYPERV to allow disabling KVM support for HyperV
     "emulation" at build time.

  ARM64:

   - LPA2 support, adding 52bit IPA/PA capability for 4kB and 16kB base
     granule sizes. Branch shared with the arm64 tree.

   - Large Fine-Grained Trap rework, bringing some sanity to the
     feature, although there is more to come. This comes with a prefix
     branch shared with the arm64 tree.

   - Some additional Nested Virtualization groundwork, mostly
     introducing the NV2 VNCR support and retargetting the NV support to
     that version of the architecture.

   - A small set of vgic fixes and associated cleanups.

  Loongarch:

   - Optimization for memslot hugepage checking

   - Cleanup and fix some HW/SW timer issues

   - Add LSX/LASX (128bit/256bit SIMD) support

  RISC-V:

   - KVM_GET_REG_LIST improvement for vector registers

   - Generate ISA extension reg_list using macros in get-reg-list
     selftest

   - Support for reporting steal time along with selftest

  s390:

   - Bugfixes

  Selftests:

   - Fix an annoying goof where the NX hugepage test prints out garbage
     instead of the magic token needed to run the test.

   - Fix build errors when a header is delete/moved due to a missing
     flag in the Makefile.

   - Detect if KVM bugged/killed a selftest's VM and print out a helpful
     message instead of complaining that a random ioctl() failed.

   - Annotate the guest printf/assert helpers with __printf(), and fix
     the various bugs that were lurking due to lack of said annotation"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (185 commits)
  x86/kvm: Do not try to disable kvmclock if it was not enabled
  KVM: x86: add missing "depends on KVM"
  KVM: fix direction of dependency on MMU notifiers
  KVM: introduce CONFIG_KVM_COMMON
  KVM: arm64: Add missing memory barriers when switching to pKVM's hyp pgd
  KVM: arm64: vgic-its: Avoid potential UAF in LPI translation cache
  RISC-V: KVM: selftests: Add get-reg-list test for STA registers
  RISC-V: KVM: selftests: Add steal_time test support
  RISC-V: KVM: selftests: Add guest_sbi_probe_extension
  RISC-V: KVM: selftests: Move sbi_ecall to processor.c
  RISC-V: KVM: Implement SBI STA extension
  RISC-V: KVM: Add support for SBI STA registers
  RISC-V: KVM: Add support for SBI extension registers
  RISC-V: KVM: Add SBI STA info to vcpu_arch
  RISC-V: KVM: Add steal-update vcpu request
  RISC-V: KVM: Add SBI STA extension skeleton
  RISC-V: paravirt: Implement steal-time support
  RISC-V: Add SBI STA extension definitions
  RISC-V: paravirt: Add skeleton for pv-time support
  RISC-V: KVM: Fix indentation in kvm_riscv_vcpu_set_reg_csr()
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kvm updates from Paolo Bonzini:
 "Generic:

   - Use memdup_array_user() to harden against overflow.

   - Unconditionally advertise KVM_CAP_DEVICE_CTRL for all
     architectures.

   - Clean up Kconfigs that all KVM architectures were selecting

   - New functionality around "guest_memfd", a new userspace API that
     creates an anonymous file and returns a file descriptor that refers
     to it. guest_memfd files are bound to their owning virtual machine,
     cannot be mapped, read, or written by userspace, and cannot be
     resized. guest_memfd files do however support PUNCH_HOLE, which can
     be used to switch a memory area between guest_memfd and regular
     anonymous memory.

   - New ioctl KVM_SET_MEMORY_ATTRIBUTES allowing userspace to specify
     per-page attributes for a given page of guest memory; right now the
     only attribute is whether the guest expects to access memory via
     guest_memfd or not, which in Confidential SVMs backed by SEV-SNP,
     TDX or ARM64 pKVM is checked by firmware or hypervisor that
     guarantees confidentiality (AMD PSP, Intel TDX module, or EL2 in
     the case of pKVM).

  x86:

   - Support for "software-protected VMs" that can use the new
     guest_memfd and page attributes infrastructure. This is mostly
     useful for testing, since there is no pKVM-like infrastructure to
     provide a meaningfully reduced TCB.

   - Fix a relatively benign off-by-one error when splitting huge pages
     during CLEAR_DIRTY_LOG.

   - Fix a bug where KVM could incorrectly test-and-clear dirty bits in
     non-leaf TDP MMU SPTEs if a racing thread replaces a huge SPTE with
     a non-huge SPTE.

   - Use more generic lockdep assertions in paths that don't actually
     care about whether the caller is a reader or a writer.

   - let Xen guests opt out of having PV clock reported as "based on a
     stable TSC", because some of them don't expect the "TSC stable" bit
     (added to the pvclock ABI by KVM, but never set by Xen) to be set.

   - Revert a bogus, made-up nested SVM consistency check for
     TLB_CONTROL.

   - Advertise flush-by-ASID support for nSVM unconditionally, as KVM
     always flushes on nested transitions, i.e. always satisfies flush
     requests. This allows running bleeding edge versions of VMware
     Workstation on top of KVM.

   - Sanity check that the CPU supports flush-by-ASID when enabling SEV
     support.

   - On AMD machines with vNMI, always rely on hardware instead of
     intercepting IRET in some cases to detect unmasking of NMIs

   - Support for virtualizing Linear Address Masking (LAM)

   - Fix a variety of vPMU bugs where KVM fail to stop/reset counters
     and other state prior to refreshing the vPMU model.

   - Fix a double-overflow PMU bug by tracking emulated counter events
     using a dedicated field instead of snapshotting the "previous"
     counter. If the hardware PMC count triggers overflow that is
     recognized in the same VM-Exit that KVM manually bumps an event
     count, KVM would pend PMIs for both the hardware-triggered overflow
     and for KVM-triggered overflow.

   - Turn off KVM_WERROR by default for all configs so that it's not
     inadvertantly enabled by non-KVM developers, which can be
     problematic for subsystems that require no regressions for W=1
     builds.

   - Advertise all of the host-supported CPUID bits that enumerate
     IA32_SPEC_CTRL "features".

   - Don't force a masterclock update when a vCPU synchronizes to the
     current TSC generation, as updating the masterclock can cause
     kvmclock's time to "jump" unexpectedly, e.g. when userspace
     hotplugs a pre-created vCPU.

   - Use RIP-relative address to read kvm_rebooting in the VM-Enter
     fault paths, partly as a super minor optimization, but mostly to
     make KVM play nice with position independent executable builds.

   - Guard KVM-on-HyperV's range-based TLB flush hooks with an #ifdef on
     CONFIG_HYPERV as a minor optimization, and to self-document the
     code.

   - Add CONFIG_KVM_HYPERV to allow disabling KVM support for HyperV
     "emulation" at build time.

  ARM64:

   - LPA2 support, adding 52bit IPA/PA capability for 4kB and 16kB base
     granule sizes. Branch shared with the arm64 tree.

   - Large Fine-Grained Trap rework, bringing some sanity to the
     feature, although there is more to come. This comes with a prefix
     branch shared with the arm64 tree.

   - Some additional Nested Virtualization groundwork, mostly
     introducing the NV2 VNCR support and retargetting the NV support to
     that version of the architecture.

   - A small set of vgic fixes and associated cleanups.

  Loongarch:

   - Optimization for memslot hugepage checking

   - Cleanup and fix some HW/SW timer issues

   - Add LSX/LASX (128bit/256bit SIMD) support

  RISC-V:

   - KVM_GET_REG_LIST improvement for vector registers

   - Generate ISA extension reg_list using macros in get-reg-list
     selftest

   - Support for reporting steal time along with selftest

  s390:

   - Bugfixes

  Selftests:

   - Fix an annoying goof where the NX hugepage test prints out garbage
     instead of the magic token needed to run the test.

   - Fix build errors when a header is delete/moved due to a missing
     flag in the Makefile.

   - Detect if KVM bugged/killed a selftest's VM and print out a helpful
     message instead of complaining that a random ioctl() failed.

   - Annotate the guest printf/assert helpers with __printf(), and fix
     the various bugs that were lurking due to lack of said annotation"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (185 commits)
  x86/kvm: Do not try to disable kvmclock if it was not enabled
  KVM: x86: add missing "depends on KVM"
  KVM: fix direction of dependency on MMU notifiers
  KVM: introduce CONFIG_KVM_COMMON
  KVM: arm64: Add missing memory barriers when switching to pKVM's hyp pgd
  KVM: arm64: vgic-its: Avoid potential UAF in LPI translation cache
  RISC-V: KVM: selftests: Add get-reg-list test for STA registers
  RISC-V: KVM: selftests: Add steal_time test support
  RISC-V: KVM: selftests: Add guest_sbi_probe_extension
  RISC-V: KVM: selftests: Move sbi_ecall to processor.c
  RISC-V: KVM: Implement SBI STA extension
  RISC-V: KVM: Add support for SBI STA registers
  RISC-V: KVM: Add support for SBI extension registers
  RISC-V: KVM: Add SBI STA info to vcpu_arch
  RISC-V: KVM: Add steal-update vcpu request
  RISC-V: KVM: Add SBI STA extension skeleton
  RISC-V: paravirt: Implement steal-time support
  RISC-V: Add SBI STA extension definitions
  RISC-V: paravirt: Add skeleton for pv-time support
  RISC-V: KVM: Fix indentation in kvm_riscv_vcpu_set_reg_csr()
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'header_cleanup-2024-01-10' of https://evilpiepirate.org/git/bcachefs</title>
<updated>2024-01-11T00:43:55+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2024-01-11T00:43:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=78273df7f646f8daf2604ec714bea0897cd03aae'/>
<id>78273df7f646f8daf2604ec714bea0897cd03aae</id>
<content type='text'>
Pull header cleanups from Kent Overstreet:
 "The goal is to get sched.h down to a type only header, so the main
  thing happening in this patchset is splitting out various _types.h
  headers and dependency fixups, as well as moving some things out of
  sched.h to better locations.

  This is prep work for the memory allocation profiling patchset which
  adds new sched.h interdepencencies"

* tag 'header_cleanup-2024-01-10' of https://evilpiepirate.org/git/bcachefs: (51 commits)
  Kill sched.h dependency on rcupdate.h
  kill unnecessary thread_info.h include
  Kill unnecessary kernel.h include
  preempt.h: Kill dependency on list.h
  rseq: Split out rseq.h from sched.h
  LoongArch: signal.c: add header file to fix build error
  restart_block: Trim includes
  lockdep: move held_lock to lockdep_types.h
  sem: Split out sem_types.h
  uidgid: Split out uidgid_types.h
  seccomp: Split out seccomp_types.h
  refcount: Split out refcount_types.h
  uapi/linux/resource.h: fix include
  x86/signal: kill dependency on time.h
  syscall_user_dispatch.h: split out *_types.h
  mm_types_task.h: Trim dependencies
  Split out irqflags_types.h
  ipc: Kill bogus dependency on spinlock.h
  shm: Slim down dependencies
  workqueue: Split out workqueue_types.h
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull header cleanups from Kent Overstreet:
 "The goal is to get sched.h down to a type only header, so the main
  thing happening in this patchset is splitting out various _types.h
  headers and dependency fixups, as well as moving some things out of
  sched.h to better locations.

  This is prep work for the memory allocation profiling patchset which
  adds new sched.h interdepencencies"

* tag 'header_cleanup-2024-01-10' of https://evilpiepirate.org/git/bcachefs: (51 commits)
  Kill sched.h dependency on rcupdate.h
  kill unnecessary thread_info.h include
  Kill unnecessary kernel.h include
  preempt.h: Kill dependency on list.h
  rseq: Split out rseq.h from sched.h
  LoongArch: signal.c: add header file to fix build error
  restart_block: Trim includes
  lockdep: move held_lock to lockdep_types.h
  sem: Split out sem_types.h
  uidgid: Split out uidgid_types.h
  seccomp: Split out seccomp_types.h
  refcount: Split out refcount_types.h
  uapi/linux/resource.h: fix include
  x86/signal: kill dependency on time.h
  syscall_user_dispatch.h: split out *_types.h
  mm_types_task.h: Trim dependencies
  Split out irqflags_types.h
  ipc: Kill bogus dependency on spinlock.h
  shm: Slim down dependencies
  workqueue: Split out workqueue_types.h
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>arch/x86: Fix typos</title>
<updated>2024-01-03T10:46:22+00:00</updated>
<author>
<name>Bjorn Helgaas</name>
<email>bhelgaas@google.com</email>
</author>
<published>2024-01-03T00:40:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=54aa699e8094efb7d7675fefbc03dfce24f98456'/>
<id>54aa699e8094efb7d7675fefbc03dfce24f98456</id>
<content type='text'>
Fix typos, most reported by "codespell arch/x86".  Only touches comments,
no code changes.

Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fix typos, most reported by "codespell arch/x86".  Only touches comments,
no code changes.

Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Link: https://lore.kernel.org/r/20240103004011.1758650-1-helgaas@kernel.org
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/signal: kill dependency on time.h</title>
<updated>2023-12-21T00:26:31+00:00</updated>
<author>
<name>Kent Overstreet</name>
<email>kent.overstreet@linux.dev</email>
</author>
<published>2023-12-11T20:08:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=34470669829761424d231156eaa57115af975b51'/>
<id>34470669829761424d231156eaa57115af975b51</id>
<content type='text'>
this is unecessary, and was pulling in printk.h from uapi headers

Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
this is unecessary, and was pulling in printk.h from uapi headers

Signed-off-by: Kent Overstreet &lt;kent.overstreet@linux.dev&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'kvm-guestmemfd' into HEAD</title>
<updated>2023-11-14T13:31:31+00:00</updated>
<author>
<name>Paolo Bonzini</name>
<email>pbonzini@redhat.com</email>
</author>
<published>2023-11-13T10:58:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=6c370dc65374db5afbc5c6c64c662f922a2555ad'/>
<id>6c370dc65374db5afbc5c6c64c662f922a2555ad</id>
<content type='text'>
Introduce several new KVM uAPIs to ultimately create a guest-first memory
subsystem within KVM, a.k.a. guest_memfd.  Guest-first memory allows KVM
to provide features, enhancements, and optimizations that are kludgly
or outright impossible to implement in a generic memory subsystem.

The core KVM ioctl() for guest_memfd is KVM_CREATE_GUEST_MEMFD, which
similar to the generic memfd_create(), creates an anonymous file and
returns a file descriptor that refers to it.  Again like "regular"
memfd files, guest_memfd files live in RAM, have volatile storage,
and are automatically released when the last reference is dropped.
The key differences between memfd files (and every other memory subystem)
is that guest_memfd files are bound to their owning virtual machine,
cannot be mapped, read, or written by userspace, and cannot be resized.
guest_memfd files do however support PUNCH_HOLE, which can be used to
convert a guest memory area between the shared and guest-private states.

A second KVM ioctl(), KVM_SET_MEMORY_ATTRIBUTES, allows userspace to
specify attributes for a given page of guest memory.  In the long term,
it will likely be extended to allow userspace to specify per-gfn RWX
protections, including allowing memory to be writable in the guest
without it also being writable in host userspace.

The immediate and driving use case for guest_memfd are Confidential
(CoCo) VMs, specifically AMD's SEV-SNP, Intel's TDX, and KVM's own pKVM.
For such use cases, being able to map memory into KVM guests without
requiring said memory to be mapped into the host is a hard requirement.
While SEV+ and TDX prevent untrusted software from reading guest private
data by encrypting guest memory, pKVM provides confidentiality and
integrity *without* relying on memory encryption.  In addition, with
SEV-SNP and especially TDX, accessing guest private memory can be fatal
to the host, i.e. KVM must be prevent host userspace from accessing
guest memory irrespective of hardware behavior.

Long term, guest_memfd may be useful for use cases beyond CoCo VMs,
for example hardening userspace against unintentional accesses to guest
memory.  As mentioned earlier, KVM's ABI uses userspace VMA protections to
define the allow guest protection (with an exception granted to mapping
guest memory executable), and similarly KVM currently requires the guest
mapping size to be a strict subset of the host userspace mapping size.
Decoupling the mappings sizes would allow userspace to precisely map
only what is needed and with the required permissions, without impacting
guest performance.

A guest-first memory subsystem also provides clearer line of sight to
things like a dedicated memory pool (for slice-of-hardware VMs) and
elimination of "struct page" (for offload setups where userspace _never_
needs to DMA from or into guest memory).

guest_memfd is the result of 3+ years of development and exploration;
taking on memory management responsibilities in KVM was not the first,
second, or even third choice for supporting CoCo VMs.  But after many
failed attempts to avoid KVM-specific backing memory, and looking at
where things ended up, it is quite clear that of all approaches tried,
guest_memfd is the simplest, most robust, and most extensible, and the
right thing to do for KVM and the kernel at-large.

The "development cycle" for this version is going to be very short;
ideally, next week I will merge it as is in kvm/next, taking this through
the KVM tree for 6.8 immediately after the end of the merge window.
The series is still based on 6.6 (plus KVM changes for 6.7) so it
will require a small fixup for changes to get_file_rcu() introduced in
6.7 by commit 0ede61d8589c ("file: convert to SLAB_TYPESAFE_BY_RCU").
The fixup will be done as part of the merge commit, and most of the text
above will become the commit message for the merge.

Pending post-merge work includes:
- hugepage support
- looking into using the restrictedmem framework for guest memory
- introducing a testing mechanism to poison memory, possibly using
  the same memory attributes introduced here
- SNP and TDX support

There are two non-KVM patches buried in the middle of this series:

  fs: Rename anon_inode_getfile_secure() and anon_inode_getfd_secure()
  mm: Add AS_UNMOVABLE to mark mapping as completely unmovable

The first is small and mostly suggested-by Christian Brauner; the second
a bit less so but it was written by an mm person (Vlastimil Babka).
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Introduce several new KVM uAPIs to ultimately create a guest-first memory
subsystem within KVM, a.k.a. guest_memfd.  Guest-first memory allows KVM
to provide features, enhancements, and optimizations that are kludgly
or outright impossible to implement in a generic memory subsystem.

The core KVM ioctl() for guest_memfd is KVM_CREATE_GUEST_MEMFD, which
similar to the generic memfd_create(), creates an anonymous file and
returns a file descriptor that refers to it.  Again like "regular"
memfd files, guest_memfd files live in RAM, have volatile storage,
and are automatically released when the last reference is dropped.
The key differences between memfd files (and every other memory subystem)
is that guest_memfd files are bound to their owning virtual machine,
cannot be mapped, read, or written by userspace, and cannot be resized.
guest_memfd files do however support PUNCH_HOLE, which can be used to
convert a guest memory area between the shared and guest-private states.

A second KVM ioctl(), KVM_SET_MEMORY_ATTRIBUTES, allows userspace to
specify attributes for a given page of guest memory.  In the long term,
it will likely be extended to allow userspace to specify per-gfn RWX
protections, including allowing memory to be writable in the guest
without it also being writable in host userspace.

The immediate and driving use case for guest_memfd are Confidential
(CoCo) VMs, specifically AMD's SEV-SNP, Intel's TDX, and KVM's own pKVM.
For such use cases, being able to map memory into KVM guests without
requiring said memory to be mapped into the host is a hard requirement.
While SEV+ and TDX prevent untrusted software from reading guest private
data by encrypting guest memory, pKVM provides confidentiality and
integrity *without* relying on memory encryption.  In addition, with
SEV-SNP and especially TDX, accessing guest private memory can be fatal
to the host, i.e. KVM must be prevent host userspace from accessing
guest memory irrespective of hardware behavior.

Long term, guest_memfd may be useful for use cases beyond CoCo VMs,
for example hardening userspace against unintentional accesses to guest
memory.  As mentioned earlier, KVM's ABI uses userspace VMA protections to
define the allow guest protection (with an exception granted to mapping
guest memory executable), and similarly KVM currently requires the guest
mapping size to be a strict subset of the host userspace mapping size.
Decoupling the mappings sizes would allow userspace to precisely map
only what is needed and with the required permissions, without impacting
guest performance.

A guest-first memory subsystem also provides clearer line of sight to
things like a dedicated memory pool (for slice-of-hardware VMs) and
elimination of "struct page" (for offload setups where userspace _never_
needs to DMA from or into guest memory).

guest_memfd is the result of 3+ years of development and exploration;
taking on memory management responsibilities in KVM was not the first,
second, or even third choice for supporting CoCo VMs.  But after many
failed attempts to avoid KVM-specific backing memory, and looking at
where things ended up, it is quite clear that of all approaches tried,
guest_memfd is the simplest, most robust, and most extensible, and the
right thing to do for KVM and the kernel at-large.

The "development cycle" for this version is going to be very short;
ideally, next week I will merge it as is in kvm/next, taking this through
the KVM tree for 6.8 immediately after the end of the merge window.
The series is still based on 6.6 (plus KVM changes for 6.7) so it
will require a small fixup for changes to get_file_rcu() introduced in
6.7 by commit 0ede61d8589c ("file: convert to SLAB_TYPESAFE_BY_RCU").
The fixup will be done as part of the merge commit, and most of the text
above will become the commit message for the merge.

Pending post-merge work includes:
- hugepage support
- looking into using the restrictedmem framework for guest memory
- introducing a testing mechanism to poison memory, possibly using
  the same memory attributes introduced here
- SNP and TDX support

There are two non-KVM patches buried in the middle of this series:

  fs: Rename anon_inode_getfile_secure() and anon_inode_getfd_secure()
  mm: Add AS_UNMOVABLE to mark mapping as completely unmovable

The first is small and mostly suggested-by Christian Brauner; the second
a bit less so but it was written by an mm person (Vlastimil Babka).
</pre>
</div>
</content>
</entry>
<entry>
<title>KVM: x86: Add support for "protected VMs" that can utilize private memory</title>
<updated>2023-11-14T13:01:05+00:00</updated>
<author>
<name>Sean Christopherson</name>
<email>seanjc@google.com</email>
</author>
<published>2023-10-27T18:22:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=89ea60c2c7b5838bf192c50062d5720cd6ab8662'/>
<id>89ea60c2c7b5838bf192c50062d5720cd6ab8662</id>
<content type='text'>
Add a new x86 VM type, KVM_X86_SW_PROTECTED_VM, to serve as a development
and testing vehicle for Confidential (CoCo) VMs, and potentially to even
become a "real" product in the distant future, e.g. a la pKVM.

The private memory support in KVM x86 is aimed at AMD's SEV-SNP and
Intel's TDX, but those technologies are extremely complex (understatement),
difficult to debug, don't support running as nested guests, and require
hardware that's isn't universally accessible.  I.e. relying SEV-SNP or TDX
for maintaining guest private memory isn't a realistic option.

At the very least, KVM_X86_SW_PROTECTED_VM will enable a variety of
selftests for guest_memfd and private memory support without requiring
unique hardware.

Signed-off-by: Sean Christopherson &lt;seanjc@google.com&gt;
Reviewed-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Message-Id: &lt;20231027182217.3615211-24-seanjc@google.com&gt;
Reviewed-by: Fuad Tabba &lt;tabba@google.com&gt;
Tested-by: Fuad Tabba &lt;tabba@google.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add a new x86 VM type, KVM_X86_SW_PROTECTED_VM, to serve as a development
and testing vehicle for Confidential (CoCo) VMs, and potentially to even
become a "real" product in the distant future, e.g. a la pKVM.

The private memory support in KVM x86 is aimed at AMD's SEV-SNP and
Intel's TDX, but those technologies are extremely complex (understatement),
difficult to debug, don't support running as nested guests, and require
hardware that's isn't universally accessible.  I.e. relying SEV-SNP or TDX
for maintaining guest private memory isn't a realistic option.

At the very least, KVM_X86_SW_PROTECTED_VM will enable a variety of
selftests for guest_memfd and private memory support without requiring
unique hardware.

Signed-off-by: Sean Christopherson &lt;seanjc@google.com&gt;
Reviewed-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Message-Id: &lt;20231027182217.3615211-24-seanjc@google.com&gt;
Reviewed-by: Fuad Tabba &lt;tabba@google.com&gt;
Tested-by: Fuad Tabba &lt;tabba@google.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>platform/x86/amd/hsmp: add support for metrics tbl</title>
<updated>2023-10-12T13:29:58+00:00</updated>
<author>
<name>Suma Hegde</name>
<email>suma.hegde@amd.com</email>
</author>
<published>2023-10-10T12:03:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=5150542b8ec5fb561be080ed0ef3bab8598154c3'/>
<id>5150542b8ec5fb561be080ed0ef3bab8598154c3</id>
<content type='text'>
AMD MI300 MCM provides GET_METRICS_TABLE message to retrieve
all the system management information from SMU.

The metrics table is made available as hexadecimal sysfs binary file
under per socket sysfs directory created at
/sys/devices/platform/amd_hsmp/socket%d/metrics_bin

Metrics table definitions will be documented as part of Public PPR.
The same is defined in the amd_hsmp.h header.

Signed-off-by: Suma Hegde &lt;suma.hegde@amd.com&gt;
Reviewed-by: Naveen Krishna Chatradhi &lt;nchatrad@amd.com&gt;
Link: https://lore.kernel.org/r/20231010120310.3464066-2-suma.hegde@amd.com
[ij: lseek -&gt; lseek(), dram -&gt; DRAM in dev_err()]
[ij: added period to terminate a documentation sentence]
Reviewed-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
AMD MI300 MCM provides GET_METRICS_TABLE message to retrieve
all the system management information from SMU.

The metrics table is made available as hexadecimal sysfs binary file
under per socket sysfs directory created at
/sys/devices/platform/amd_hsmp/socket%d/metrics_bin

Metrics table definitions will be documented as part of Public PPR.
The same is defined in the amd_hsmp.h header.

Signed-off-by: Suma Hegde &lt;suma.hegde@amd.com&gt;
Reviewed-by: Naveen Krishna Chatradhi &lt;nchatrad@amd.com&gt;
Link: https://lore.kernel.org/r/20231010120310.3464066-2-suma.hegde@amd.com
[ij: lseek -&gt; lseek(), dram -&gt; DRAM in dev_err()]
[ij: added period to terminate a documentation sentence]
Reviewed-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
Signed-off-by: Ilpo Järvinen &lt;ilpo.jarvinen@linux.intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86: Remove the arch_calc_vm_prot_bits() macro from the UAPI</title>
<updated>2023-09-06T21:50:46+00:00</updated>
<author>
<name>Thomas Huth</name>
<email>thuth@redhat.com</email>
</author>
<published>2023-09-06T16:26:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=659df86a7b2fe98feb5f4ec880e694caaebd27ae'/>
<id>659df86a7b2fe98feb5f4ec880e694caaebd27ae</id>
<content type='text'>
The arch_calc_vm_prot_bits() macro uses VM_PKEY_BIT0 etc. which are
not part of the UAPI, so the macro is completely useless for userspace.

It is also hidden behind the CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
config switch which we shouldn't expose to userspace. Thus let's move
this macro into a new internal header instead.

Fixes: 8f62c883222c ("x86/mm/pkeys: Add arch-specific VMA protection bits")
Signed-off-by: Thomas Huth &lt;thuth@redhat.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Reviewed-by: Nicolas Schier &lt;nicolas@fjasle.eu&gt;
Acked-by: Dave Hansen &lt;dave.hansen@intel.com&gt;
Link: https://lore.kernel.org/r/20230906162658.142511-1-thuth@redhat.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The arch_calc_vm_prot_bits() macro uses VM_PKEY_BIT0 etc. which are
not part of the UAPI, so the macro is completely useless for userspace.

It is also hidden behind the CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
config switch which we shouldn't expose to userspace. Thus let's move
this macro into a new internal header instead.

Fixes: 8f62c883222c ("x86/mm/pkeys: Add arch-specific VMA protection bits")
Signed-off-by: Thomas Huth &lt;thuth@redhat.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Reviewed-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Reviewed-by: Nicolas Schier &lt;nicolas@fjasle.eu&gt;
Acked-by: Dave Hansen &lt;dave.hansen@intel.com&gt;
Link: https://lore.kernel.org/r/20230906162658.142511-1-thuth@redhat.com
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/shstk: Add ARCH_SHSTK_STATUS</title>
<updated>2023-08-02T22:01:51+00:00</updated>
<author>
<name>Rick Edgecombe</name>
<email>rick.p.edgecombe@intel.com</email>
</author>
<published>2023-06-13T00:11:08+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=67840ad0fa14ad49a605074b12d5b0f3c3113ed1'/>
<id>67840ad0fa14ad49a605074b12d5b0f3c3113ed1</id>
<content type='text'>
CRIU and GDB need to get the current shadow stack and WRSS enablement
status. This information is already available via /proc/pid/status, but
this is inconvenient for CRIU because it involves parsing the text output
in an area of the code where this is difficult. Provide a status
arch_prctl(), ARCH_SHSTK_STATUS for retrieving the status. Have arg2 be a
userspace address, and make the new arch_prctl simply copy the features
out to userspace.

Suggested-by: Mike Rapoport &lt;rppt@kernel.org&gt;
Signed-off-by: Rick Edgecombe &lt;rick.p.edgecombe@intel.com&gt;
Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Reviewed-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Acked-by: Mike Rapoport (IBM) &lt;rppt@kernel.org&gt;
Tested-by: Pengfei Xu &lt;pengfei.xu@intel.com&gt;
Tested-by: John Allen &lt;john.allen@amd.com&gt;
Tested-by: Kees Cook &lt;keescook@chromium.org&gt;
Link: https://lore.kernel.org/all/20230613001108.3040476-43-rick.p.edgecombe%40intel.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
CRIU and GDB need to get the current shadow stack and WRSS enablement
status. This information is already available via /proc/pid/status, but
this is inconvenient for CRIU because it involves parsing the text output
in an area of the code where this is difficult. Provide a status
arch_prctl(), ARCH_SHSTK_STATUS for retrieving the status. Have arg2 be a
userspace address, and make the new arch_prctl simply copy the features
out to userspace.

Suggested-by: Mike Rapoport &lt;rppt@kernel.org&gt;
Signed-off-by: Rick Edgecombe &lt;rick.p.edgecombe@intel.com&gt;
Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Reviewed-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Acked-by: Mike Rapoport (IBM) &lt;rppt@kernel.org&gt;
Tested-by: Pengfei Xu &lt;pengfei.xu@intel.com&gt;
Tested-by: John Allen &lt;john.allen@amd.com&gt;
Tested-by: Kees Cook &lt;keescook@chromium.org&gt;
Link: https://lore.kernel.org/all/20230613001108.3040476-43-rick.p.edgecombe%40intel.com
</pre>
</div>
</content>
</entry>
<entry>
<title>x86/shstk: Add ARCH_SHSTK_UNLOCK</title>
<updated>2023-08-02T22:01:51+00:00</updated>
<author>
<name>Mike Rapoport</name>
<email>rppt@linux.ibm.com</email>
</author>
<published>2023-06-13T00:11:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=680ed2f15e70d079c8148589a3ce9426fc0ff914'/>
<id>680ed2f15e70d079c8148589a3ce9426fc0ff914</id>
<content type='text'>
Userspace loaders may lock features before a CRIU restore operation has
the chance to set them to whatever state is required by the process
being restored. Allow a way for CRIU to unlock features. Add it as an
arch_prctl() like the other shadow stack operations, but restrict it being
called by the ptrace arch_pctl() interface.

[Merged into recent API changes, added commit log and docs]

Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Signed-off-by: Rick Edgecombe &lt;rick.p.edgecombe@intel.com&gt;
Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Reviewed-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Tested-by: Pengfei Xu &lt;pengfei.xu@intel.com&gt;
Tested-by: John Allen &lt;john.allen@amd.com&gt;
Tested-by: Kees Cook &lt;keescook@chromium.org&gt;
Link: https://lore.kernel.org/all/20230613001108.3040476-42-rick.p.edgecombe%40intel.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Userspace loaders may lock features before a CRIU restore operation has
the chance to set them to whatever state is required by the process
being restored. Allow a way for CRIU to unlock features. Add it as an
arch_prctl() like the other shadow stack operations, but restrict it being
called by the ptrace arch_pctl() interface.

[Merged into recent API changes, added commit log and docs]

Signed-off-by: Mike Rapoport &lt;rppt@linux.ibm.com&gt;
Signed-off-by: Rick Edgecombe &lt;rick.p.edgecombe@intel.com&gt;
Signed-off-by: Dave Hansen &lt;dave.hansen@linux.intel.com&gt;
Reviewed-by: Borislav Petkov (AMD) &lt;bp@alien8.de&gt;
Reviewed-by: Kees Cook &lt;keescook@chromium.org&gt;
Reviewed-by: David Hildenbrand &lt;david@redhat.com&gt;
Tested-by: Pengfei Xu &lt;pengfei.xu@intel.com&gt;
Tested-by: John Allen &lt;john.allen@amd.com&gt;
Tested-by: Kees Cook &lt;keescook@chromium.org&gt;
Link: https://lore.kernel.org/all/20230613001108.3040476-42-rick.p.edgecombe%40intel.com
</pre>
</div>
</content>
</entry>
</feed>
