Re: [Patch v3 0/4] Protect against concurrent calls into UV BIOS
From: Dimitri Sivanich
Date: Thu Feb 14 2019 - 16:22:10 EST
For the series:
Reviewed-by: Dimitri Sivanich <sivanich@xxxxxxx>
On Wed, Feb 13, 2019 at 07:34:09PM +0000, Hedi Berriche wrote:
> - Changes since v2
> Addressed comments from Ard Biesheuvel:
> * expose efi_runtime_lock to UV platform only instead of globally
> * remove unnecessary #ifdef CONFIG_EFI from bios_uv.c
> - Changes since v1:
> Addressed comments from Bhupesh Sharma, Thomas Gleixner, and Ard Biesheuvel:
> * made __uv_bios_call() static
> * moved the efi_enabled() cleanup to its own patchlet
> * explained the reason for renaming the efi_runtime_lock semaphore
> * dropped the reviewed-bys as they should be given on the mailing list
> * Cc'ng stable@xxxxxxxxxxxxxxx given the nature of the problem addressed by the patches
> Calls into UV BIOS were not being serialised which is wrong as it violates EFI
> runtime rules, and bad as it does result in all sorts of potentially hard to
> track down hangs and panics when efi_scratch.prev_mm gets clobbered whenever
> efi_switch_mm() gets called concurrently from two different CPUs.
> Patch #1 removes an unnecessary #ifdef CONFIG_EFI guard from bios_uv.c.
> Patch #2 removes uv_bios_call_reentrant() because it's dead code.
> Patch #3 is a cleanup that drops test_bit() in favour of the ad hoc efi_enabled().
> Patch #4 makes uv_bios_call() variants use the efi_runtime_lock semaphore to
> protect against concurrency.
> Cc: Russ Anderson <rja@xxxxxxx>
> Cc: Mike Travis <mike.travis@xxxxxxx>
> Cc: Dimitri Sivanich <sivanich@xxxxxxx>
> Cc: Steve Wahl <steve.wahl@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v4.9+
> Hedi Berriche (4):
> x86/platform/UV: remove unnecessary #ifdef CONFIG_EFI
> x86/platform/UV: kill uv_bios_call_reentrant() as it has no callers
> x86/platform/UV: use efi_enabled() instead of test_bit()
> x86/platform/UV: use efi_runtime_lock to serialise BIOS calls
> arch/x86/include/asm/uv/bios.h | 13 ++++-----
> arch/x86/platform/uv/bios_uv.c | 35 ++++++++++++++-----------
> drivers/firmware/efi/runtime-wrappers.c | 7 +++++
> 3 files changed, 34 insertions(+), 21 deletions(-)