linux-stable.git/arch/powerpc/kernel, branch v5.4.296

powerpc/eeh: Fix missing PE bridge reconfiguration during VFIO EEH recovery

2025-06-27T10:02:56+00:00

[ Upstream commit 33bc69cf6655cf60829a803a45275f11a74899e5 ]

VFIO EEH recovery for PCI passthrough devices fails on PowerNV and pseries
platforms due to missing host-side PE bridge reconfiguration. In the
current implementation, eeh_pe_configure() only performs RTAS or OPAL-based
bridge reconfiguration for native host devices, but skips it entirely for
PEs managed through VFIO in guest passthrough scenarios.

This leads to incomplete EEH recovery when a PCI error affects a
passthrough device assigned to a QEMU/KVM guest. Although VFIO triggers the
EEH recovery flow through VFIO_EEH_PE_ENABLE ioctl, the platform-specific
bridge reconfiguration step is silently bypassed. As a result, the PE's
config space is not fully restored, causing subsequent config space access
failures or EEH freeze-on-access errors inside the guest.

This patch fixes the issue by ensuring that eeh_pe_configure() always
invokes the platform's configure_bridge() callback (e.g.,
pseries_eeh_phb_configure_bridge) even for VFIO-managed PEs. This ensures
that RTAS or OPAL calls to reconfigure the PE bridge are correctly issued
on the host side, restoring the PE's configuration space after an EEH
event.

This fix is essential for reliable EEH recovery in QEMU/KVM guests using
VFIO PCI passthrough on PowerNV and pseries systems.

Tested with:
- QEMU/KVM guest using VFIO passthrough (IBM Power9,(lpar)Power11 host)
- Injected EEH errors with pseries EEH errinjct tool on host, recovery
  verified on qemu guest.
- Verified successful config space access and CAP_EXP DevCtl restoration
  after recovery

Fixes: 212d16cdca2d ("powerpc/eeh: EEH support for VFIO PCI device")
Signed-off-by: Narayana Murty N 
Reviewed-by: Vaibhav Jain 
Reviewed-by: Ganesh Goudar 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20250508062928.146043-1-nnmlinux@linux.ibm.com
Signed-off-by: Sasha Levin

powerpc/prom_init: Fixup missing #size-cells on PowerBook6,7

2025-06-04T12:32:31+00:00

[ Upstream commit 7e67ef889c9ab7246547db73d524459f47403a77 ]

Similar to the PowerMac3,1, the PowerBook6,7 is missing the #size-cells
property on the i2s node.

Depends-on: commit 045b14ca5c36 ("of: WARN on deprecated #address-cells/#size-cells handling")
Signed-off-by: Andreas Schwab 
Acked-by: Rob Herring (Arm) 
[maddy: added "commit" work in depends-on to avoid checkpatch error]
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/875xmizl6a.fsf@igel.home
Signed-off-by: Sasha Levin

powerpc/prom_init: Use -ffreestanding to avoid a reference to bcmp

2025-05-02T05:39:22+00:00

commit 8dcd71b45df34d9b903450fab147ee8c1e6c16b5 upstream.

LLVM revision r374662 gives LLVM the ability to convert certain loops
into a reference to bcmp as an optimization; this breaks
prom_init_check.sh:

    CALL    arch/powerpc/kernel/prom_init_check.sh
  Error: External symbol 'bcmp' referenced from prom_init.c
  make[2]: *** [arch/powerpc/kernel/Makefile:196: prom_init_check] Error 1

bcmp is defined in lib/string.c as a wrapper for memcmp so this could
be added to the whitelist. However, commit
450e7dd4001f ("powerpc/prom_init: don't use string functions from
lib/") copied memcmp as prom_memcmp to avoid KASAN instrumentation so
having bcmp be resolved to regular memcmp would break that assumption.
Furthermore, because the compiler is the one that inserted bcmp, we
cannot provide something like prom_bcmp.

To prevent LLVM from being clever with optimizations like this, use
-ffreestanding to tell LLVM we are not hosted so it is not free to
make transformations like this.

Reviewed-by: Nick Desaulneris 
Signed-off-by: Nathan Chancellor 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20191119045712.39633-4-natechancellor@gmail.com
Signed-off-by: Greg Kroah-Hartman

powerpc/prom_init: Fixup missing powermac #size-cells

2024-12-14T18:44:54+00:00

[ Upstream commit cf89c9434af122f28a3552e6f9cc5158c33ce50a ]

On some powermacs `escc` nodes are missing `#size-cells` properties,
which is deprecated and now triggers a warning at boot since commit
045b14ca5c36 ("of: WARN on deprecated #address-cells/#size-cells
handling").

For example:

  Missing '#size-cells' in /pci@f2000000/mac-io@c/escc@13000
  WARNING: CPU: 0 PID: 0 at drivers/of/base.c:133 of_bus_n_size_cells+0x98/0x108
  Hardware name: PowerMac3,1 7400 0xc0209 PowerMac
  ...
  Call Trace:
    of_bus_n_size_cells+0x98/0x108 (unreliable)
    of_bus_default_count_cells+0x40/0x60
    __of_get_address+0xc8/0x21c
    __of_address_to_resource+0x5c/0x228
    pmz_init_port+0x5c/0x2ec
    pmz_probe.isra.0+0x144/0x1e4
    pmz_console_init+0x10/0x48
    console_init+0xcc/0x138
    start_kernel+0x5c4/0x694

As powermacs boot via prom_init it's possible to add the missing
properties to the device tree during boot, avoiding the warning. Note
that `escc-legacy` nodes are also missing `#size-cells` properties, but
they are skipped by the macio driver, so leave them alone.

Depends-on: 045b14ca5c36 ("of: WARN on deprecated #address-cells/#size-cells handling")
Signed-off-by: Michael Ellerman 
Reviewed-by: Rob Herring 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20241126025710.591683-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin

powerpc/eeh: avoid possible crash when edev->pdev changes

2024-07-27T08:38:31+00:00

[ Upstream commit a1216e62d039bf63a539bbe718536ec789a853dd ]

If a PCI device is removed during eeh_pe_report_edev(), edev->pdev
will change and can cause a crash, hold the PCI rescan/remove lock
while taking a copy of edev->pdev->bus.

Signed-off-by: Ganesh Goudar 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20240617140240.580453-1-ganeshgr@linux.ibm.com
Signed-off-by: Sasha Levin

powerpc: Fix build error due to is_valid_bugaddr()

2024-02-23T07:24:53+00:00

[ Upstream commit f8d3555355653848082c351fa90775214fb8a4fa ]

With CONFIG_GENERIC_BUG=n the build fails with:

  arch/powerpc/kernel/traps.c:1442:5: error: no previous prototype for ‘is_valid_bugaddr’ [-Werror=missing-prototypes]
  1442 | int is_valid_bugaddr(unsigned long addr)
       |     ^~~~~~~~~~~~~~~~

The prototype is only defined, and the function is only needed, when
CONFIG_GENERIC_BUG=y, so move the implementation under that.

Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20231130114433.3053544-2-mpe@ellerman.id.au
Signed-off-by: Sasha Levin

powerpc/ftrace: Fix stack teardown in ftrace_no_trace

2023-12-20T14:41:26+00:00

commit 4b3338aaa74d7d4ec5b6734dc298f0db94ec83d2 upstream.

Commit 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix
stack unwind") added use of a new stack frame on ftrace entry to fix
stack unwind. However, the commit missed updating the offset used while
tearing down the ftrace stack when ftrace is disabled. Fix the same.

In addition, the commit missed saving the correct stack pointer in
pt_regs. Update the same.

Fixes: 41a506ef71eb ("powerpc/ftrace: Create a dummy stackframe to fix stack unwind")
Cc: stable@vger.kernel.org # v6.5+
Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20231130065947.2188860-1-naveen@kernel.org
Signed-off-by: Greg Kroah-Hartman

powerpc/ftrace: Create a dummy stackframe to fix stack unwind

2023-12-20T14:41:26+00:00

commit 41a506ef71eb38d94fe133f565c87c3e06ccc072 upstream.

With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to
call into ftrace are emitted right at function entry. The instruction
sequence used is minimal to reduce overhead. Crucially, a stackframe is
not created for the function being traced. This breaks stack unwinding
since the function being traced does not have a stackframe for itself.
As such, it never shows up in the backtrace:

/sys/kernel/debug/tracing # echo 1 > /proc/sys/kernel/stack_tracer_enabled
/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     4144      32   ftrace_call+0x4/0x44
  1)     4112     432   get_page_from_freelist+0x26c/0x1ad0
  2)     3680     496   __alloc_pages+0x290/0x1280
  3)     3184     336   __folio_alloc+0x34/0x90
  4)     2848     176   vma_alloc_folio+0xd8/0x540
  5)     2672     272   __handle_mm_fault+0x700/0x1cc0
  6)     2400     208   handle_mm_fault+0xf0/0x3f0
  7)     2192      80   ___do_page_fault+0x3e4/0xbe0
  8)     2112     160   do_page_fault+0x30/0xc0
  9)     1952     256   data_access_common_virt+0x210/0x220
 10)     1696     400   0xc00000000f16b100
 11)     1296     384   load_elf_binary+0x804/0x1b80
 12)      912     208   bprm_execve+0x2d8/0x7e0
 13)      704      64   do_execveat_common+0x1d0/0x2f0
 14)      640     160   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

Fix this by having ftrace create a dummy stackframe for the function
being traced. With this, backtraces now capture the function being
traced:

/sys/kernel/debug/tracing # cat stack_trace
        Depth    Size   Location    (17 entries)
        -----    ----   --------
  0)     3888      32   _raw_spin_trylock+0x8/0x70
  1)     3856     576   get_page_from_freelist+0x26c/0x1ad0
  2)     3280      64   __alloc_pages+0x290/0x1280
  3)     3216     336   __folio_alloc+0x34/0x90
  4)     2880     176   vma_alloc_folio+0xd8/0x540
  5)     2704     416   __handle_mm_fault+0x700/0x1cc0
  6)     2288      96   handle_mm_fault+0xf0/0x3f0
  7)     2192      48   ___do_page_fault+0x3e4/0xbe0
  8)     2144     192   do_page_fault+0x30/0xc0
  9)     1952     608   data_access_common_virt+0x210/0x220
 10)     1344      16   0xc0000000334bbb50
 11)     1328     416   load_elf_binary+0x804/0x1b80
 12)      912      64   bprm_execve+0x2d8/0x7e0
 13)      848     176   do_execveat_common+0x1d0/0x2f0
 14)      672     192   sys_execve+0x54/0x70
 15)      480      64   system_call_exception+0x138/0x350
 16)      416     416   system_call_common+0x160/0x2c4

This results in two additional stores in the ftrace entry code, but
produces reliable backtraces.

Fixes: 153086644fd1 ("powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI")
Cc: stable@vger.kernel.org
Signed-off-by: Naveen N Rao 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230621051349.759567-1-naveen@kernel.org
Signed-off-by: Greg Kroah-Hartman

powerpc: Don't clobber f0/vs0 during fp|altivec register save

2023-12-08T07:44:26+00:00

commit 5e1d824f9a283cbf90f25241b66d1f69adb3835b upstream.

During floating point and vector save to thread data f0/vs0 are
clobbered by the FPSCR/VSCR store routine. This has been obvserved to
lead to userspace register corruption and application data corruption
with io-uring.

Fix it by restoring f0/vs0 after FPSCR/VSCR store has completed for
all the FP, altivec, VMX register save paths.

Tested under QEMU in kvm mode, running on a Talos II workstation with
dual POWER9 DD2.2 CPUs.

Additional detail (mpe):

Typically save_fpu() is called from __giveup_fpu() which saves the FP
regs and also *turns off FP* in the tasks MSR, meaning the kernel will
reload the FP regs from the thread struct before letting the task use FP
again. So in that case save_fpu() is free to clobber f0 because the FP
regs no longer hold live values for the task.

There is another case though, which is the path via:
  sys_clone()
    ...
    copy_process()
      dup_task_struct()
        arch_dup_task_struct()
          flush_all_to_thread()
            save_all()

That path saves the FP regs but leaves them live. That's meant as an
optimisation for a process that's using FP/VSX and then calls fork(),
leaving the regs live means the parent process doesn't have to take a
fault after the fork to get its FP regs back. The optimisation was added
in commit 8792468da5e1 ("powerpc: Add the ability to save FPU without
giving it up").

That path does clobber f0, but f0 is volatile across function calls,
and typically programs reach copy_process() from userspace via a syscall
wrapper function. So in normal usage f0 being clobbered across a
syscall doesn't cause visible data corruption.

But there is now a new path, because io-uring can call copy_process()
via create_io_thread() from the signal handling path. That's OK if the
signal is handled as part of syscall return, but it's not OK if the
signal is handled due to some other interrupt.

That path is:

interrupt_return_srr_user()
  interrupt_exit_user_prepare()
    interrupt_exit_user_prepare_main()
      do_notify_resume()
        get_signal()
          task_work_run()
            create_worker_cb()
              create_io_worker()
                copy_process()
                  dup_task_struct()
                    arch_dup_task_struct()
                      flush_all_to_thread()
                        save_all()
                          if (tsk->thread.regs->msr & MSR_FP)
                            save_fpu()
                            # f0 is clobbered and potentially live in userspace

Note the above discussion applies equally to save_altivec().

Fixes: 8792468da5e1 ("powerpc: Add the ability to save FPU without giving it up")
Cc: stable@vger.kernel.org # v4.6+
Closes: https://lore.kernel.org/all/480932026.45576726.1699374859845.JavaMail.zimbra@raptorengineeringinc.com/
Closes: https://lore.kernel.org/linuxppc-dev/480221078.47953493.1700206777956.JavaMail.zimbra@raptorengineeringinc.com/
Tested-by: Timothy Pearson 
Tested-by: Jens Axboe 
Signed-off-by: Timothy Pearson 
[mpe: Reword change log to describe exact path of corruption & other minor tweaks]
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/1921539696.48534988.1700407082933.JavaMail.zimbra@raptorengineeringinc.com
Signed-off-by: Greg Kroah-Hartman

powerpc/watchpoints: Annotate atomic context in more places

2023-10-10T19:46:40+00:00

[ Upstream commit 27646b2e02b096a6936b3e3b6ba334ae20763eab ]

It can be easy to miss that the notifier mechanism invokes the callbacks
in an atomic context, so add some comments to that effect on the two
handlers we register here.

Signed-off-by: Benjamin Gray 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230829063457.54157-4-bgray@linux.ibm.com
Signed-off-by: Sasha Levin