From: Dave Hansen <dave.hansen@intel.com>
To: Brian Geffon <bgeffon@google.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Willis Kung <williskung@google.com>,
Guenter Roeck <groeck@google.com>, Borislav Petkov <bp@suse.de>,
Andy Lutomirski <luto@kernel.org>,
"# v4 . 10+" <stable@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH stable 5.4,5.10] x86/fpu: Correct pkru/xstate inconsistency
Date: Thu, 17 Feb 2022 08:44:17 -0800 [thread overview]
Message-ID: <dbe8b78e-bc55-c796-358f-a93e0eac87d1@intel.com> (raw)
In-Reply-To: <CADyq12yGvqbb3+hp6f39RqyEM3Mu896yY6ik7Lh39W=o44bYbA@mail.gmail.com>
On 2/17/22 05:31, Brian Geffon wrote:
> How would you and Greg KH like to proceed with this? I'm happy to help
> however I can.
If I could wave a magic wand, I'd just apply the whole FPU rewrite to
stable.
My second choice would be to stop managing PKRU with XSAVE.
x86_pkru_load() uses WRPKRU instead of XSAVE and keeps the task's PKRU
in task->pkru instead of the XSAVE buffer. Doing that will take some
care, including pulling XFEATURE_PKRU out of the feature mask (RFBM) at
XRSTOR. I _think_ that can be done in a manageable set of patches which
will keep stable close to mainline. I recognize that more bugs might
get introduced in the process which are unique to stable.
If you give that a shot and realize that it's not feasible to do a
subset, then we can fall back to the minimal fix. I'm not asking for a
multi-month engineering effort here. Maybe an hour or two to see if
it's really as scary as it looks.
next prev parent reply other threads:[~2022-02-17 16:44 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-15 15:36 [PATCH] x86/fpu: Correct pkru/xstate inconsistency Brian Geffon
2022-02-15 15:57 ` Guenter Roeck
2022-02-15 16:19 ` Brian Geffon
2022-02-15 17:02 ` Guenter Roeck
2022-02-15 17:10 ` Dave Hansen
2022-02-15 16:20 ` Greg KH
2022-02-15 17:07 ` Dave Hansen
2022-02-15 17:50 ` Brian Geffon
2022-02-15 17:55 ` Dave Hansen
2022-02-15 19:22 ` [PATCH stable 5.4,5.10] " Brian Geffon
2022-02-15 19:44 ` Greg KH
2022-02-15 21:32 ` Brian Geffon
2022-02-15 21:42 ` Dave Hansen
2022-02-15 21:48 ` Brian Geffon
2022-02-16 2:01 ` Brian Geffon
2022-02-16 10:05 ` Greg KH
2022-02-16 10:05 ` Greg KH
2022-02-16 15:14 ` Brian Geffon
2022-02-16 15:16 ` Dave Hansen
2022-02-17 13:31 ` Brian Geffon
2022-02-17 16:44 ` Dave Hansen [this message]
2022-02-17 20:42 ` Brian Geffon
2022-02-24 15:16 ` Dave Hansen
2022-02-25 12:01 ` Greg KH
2022-02-15 21:14 ` [PATCH] " Guenter Roeck
2022-02-15 21:36 ` Brian Geffon
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