linux-kernel - Re: [PATCH v3 0/7] x86: Pile o' FS/GS changes

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Date:	Fri, 8 Apr 2016 12:40:40 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	security@...nel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rudolf Marek <r.marek@...embler.cz>
Subject: Re: [PATCH v3 0/7] x86: Pile o' FS/GS changes

On Thu, Apr 07, 2016 at 05:31:43PM -0700, Andy Lutomirski wrote:
> Hi all-
> 
> This whole mess is intended for x86/urgent.  It fixes several bugs.
> 
> It's probably a tiny performance regression on some workloads on
> Intel CPUs.  It's probably varies between a less tiny regression and
> a small speedup on newer AMD CPUs.  It's a bigger regression on AMD
> K8.
> 
> The AMD code could be further sped up by adding a new 'clear_gs'
> pvop with a better native implementation.  I don't particularly want
> to deal with a backported new pvop, so I didn't do that.  Maybe I'll
> do it later on for new kernels, though.
> 
> (For people who care about such things, there are probably three
> bugs in here depending how you count.  Somewhere between one and two
> of them were independently discovered by Rudolf Marek.)
> 
> Andy Lutomirski (5):
>   selftests/x86: Test the FSBASE/GSBASE API and context switching
>   x86/arch_prctl: Fix ARCH_GET_FS and ARCH_GET_GS
>   x86/cpu: Probe the behavior of nulling out a segment at boot time
>   x86/switch_to: Rewrite the FS and GS context switch code
>   x86/cpu: Move X86_BUG_ESPFIX initialization to generic_identify
> 
> Borislav Petkov (2):
>   x86/cpu: Add Erratum 88 detection on AMD
>   x86/entry: Make gs_change a local label
> 
>  arch/x86/entry/entry_64.S              |  12 +-
>  arch/x86/include/asm/cpufeatures.h     |   3 +
>  arch/x86/kernel/cpu/amd.c              |   1 +
>  arch/x86/kernel/cpu/common.c           |  71 ++++--
>  arch/x86/kernel/process_64.c           | 167 ++++++++------
>  tools/testing/selftests/x86/Makefile   |   1 +
>  tools/testing/selftests/x86/fsgsbase.c | 398 +++++++++++++++++++++++++++++++++
>  7 files changed, 560 insertions(+), 93 deletions(-)
>  create mode 100644 tools/testing/selftests/x86/fsgsbase.c

Forgot to add:

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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