linux-kernel - Re: [patch V3 00/66] x86/fpu: Spring cleaning and PKRU sanitizing

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Date:   Wed, 23 Jun 2021 00:26:14 +0530
From:   "Dey, Megha" <megha.dey@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [patch V3 00/66] x86/fpu: Spring cleaning and PKRU sanitizing

Hi Thomas,

On 6/18/2021 7:48 PM, Thomas Gleixner wrote:
> The main parts of this series are:
> 
>    - Yet more bug fixes
> 
>    - Simplification and removal/replacement of redundant and/or
>      overengineered code.
> 
>    - Name space cleanup as the existing names were just a permanent source
>      of confusion.
> 
>    - Clear seperation of user ABI and kernel internal state handling.
> 
>    - Removal of PKRU from being XSTATE managed in the kernel because PKRU
>      has to be eagerly restored on context switch and keeping it in sync
>      in the xstate buffer is just pointless overhead and fragile.
> 
>      The kernel still XSAVEs PKRU on context switch but the value in the
>      buffer is not longer used and never restored from the buffer.
> 
>      This still needs to be cleaned up, but the series is already 40+
>      patches large and the cleanup of this is not a functional problem.
> 
>      The functional issues of PKRU management are fully addressed with the
>      series as is.
> 
>    - Cleanup of fpu signal restore
> 
>      - Make the fast path self contained. Handle #PF directly and skip
>        the slow path on any other exception as that will just end up
>        with the same result that the frame is invalid. This allows
>        the compiler to optimize the slow path out for 64bit kernels
>        w/o ia32 emulation.
> 
>      - Reduce code duplication and unnecessary operations
>        
> 
> It applies on top of
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git master
> 
> and is also available via git:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git x86/fpu
> 
> This is a follow up to V2 which can be found here:
> 
>       https://lore.kernel.org/r/20210614154408.673478623@linutronix.de

I tested the x86/fpu branch using both AVX2(intree) and AVX512(out of 
tree) crypto code.

I used the tcrypt test module in the kernel and ran the prime95 workload 
(which finds prime numbers using AVX2 or AVX512) as a background process 
to make sure that the AVX states don't get screwed up after we run the 
crypto in kernel.

I did not see any issues with this branch and all tcrypt tests run as 
expected. I tested using the SHA1/256, AES-CTR, AES-GCM, camelia and 
crc32t10diff crypto algorithms.

Thanks,
Megha

> 
> Changes vs. V2:
> 
>    - Fixed the testing fallout (Dave, Kan)
> 
>    - Fixed a few issues found by myself when going through the lot
>      with a fine comb, especially MXCSR handling
> 
>    - Drop the FNSAVE optimizations
> 
>    - Cleanup of signal restore
> 
>    - Addressed review comments, mostly comments and a hopefully better
>      naming scheme which now just uses the instruction names and
>      consolidates everything else on save/restore so it's close to the way
>      how the hardware works.
> 
>    - A few cleanups and simplifications on the way (mostly regset related).
> 
>    - Picked up tags
> 
> With the above I'm not intending to do any further surgery on that
> code at the moment, though there is still room for improvement which
> can and has to be worked on when new bits are added.
> 
> Thanks,
> 
> 	tglx
> ---
>   arch/x86/events/intel/lbr.c          |    6
>   arch/x86/include/asm/fpu/internal.h  |  211 +++-------
>   arch/x86/include/asm/fpu/xstate.h    |   70 ++-
>   arch/x86/include/asm/pgtable.h       |   57 --
>   arch/x86/include/asm/pkeys.h         |    9
>   arch/x86/include/asm/pkru.h          |   62 +++
>   arch/x86/include/asm/processor.h     |    9
>   arch/x86/include/asm/special_insns.h |   14
>   arch/x86/kernel/cpu/common.c         |   34 -
>   arch/x86/kernel/fpu/core.c           |  276 +++++++------
>   arch/x86/kernel/fpu/init.c           |   15
>   arch/x86/kernel/fpu/regset.c         |  220 ++++++-----
>   arch/x86/kernel/fpu/signal.c         |  423 +++++++++------------
>   arch/x86/kernel/fpu/xstate.c         |  693 ++++++++++++++---------------------
>   arch/x86/kernel/process.c            |   22 -
>   arch/x86/kernel/process_64.c         |   28 +
>   arch/x86/kernel/traps.c              |    5
>   arch/x86/kvm/svm/sev.c               |    1
>   arch/x86/kvm/x86.c                   |   56 +-
>   arch/x86/mm/extable.c                |    2
>   arch/x86/mm/fault.c                  |    2
>   arch/x86/mm/pkeys.c                  |   22 -
>   include/linux/pkeys.h                |    4
>   23 files changed, 1060 insertions(+), 1181 deletions(-)
> 
>