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From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: "Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	"Andy Lutomirski" <luto@kernel.org>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
	"Rik van Riel" <riel@surriel.com>
Subject: Re: [RFC PATCH 04/10] x86/fpu: eager switch PKRU state
Date: Wed, 12 Sep 2018 17:30:49 +0200	[thread overview]
Message-ID: <823a0f8e-5c08-cd4d-851b-9e8e147fe01b@redhat.com> (raw)
In-Reply-To: <3476ED25-96C7-4285-AF1D-7FB82E10FB6C@amacapital.net>

On 12/09/2018 17:24, Andy Lutomirski wrote:
>> I think you can go a step further and exclude PKRU state from
>> copy_kernel_to_fpregs altogether; you just use RDPKRU/WRPKRU.  This also
>> means you don't need to call __fpregs_* functions in write_pkru.
>>
>>
> Except that the signal ABI has PKRU in the xstate. So we’d need to fake it or do something special for signals.

The signal ABI is already special because it uses the non-compacted
format.  As long as copy_fpregs_to_sigframe includes the PKRU state
(i.e. EDX:EAX=-1), and PKRU value is okay (which it is because it's
switched eagerly), everything should work...

Paolo

  reply	other threads:[~2018-09-12 15:30 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-12 13:33 [RFC PATCH] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 01/10] x86/entry: remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-09-27 14:21   ` Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 02/10] kvm: x86: make kvm_{load|put}_guest_fpu() static Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 03/10] x86/fpu: add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 04/10] x86/fpu: eager switch PKRU state Sebastian Andrzej Siewior
2018-09-12 14:18   ` Paolo Bonzini
2018-09-12 15:24     ` Andy Lutomirski
2018-09-12 15:30       ` Paolo Bonzini [this message]
2018-09-14 20:35     ` [RFC PATCH 04/10 v2 ] " Sebastian Andrzej Siewior
2018-09-17  8:37       ` Paolo Bonzini
2018-09-18 14:27         ` Sebastian Andrzej Siewior
2018-09-18 15:07           ` Paolo Bonzini
2018-09-18 15:11             ` Rik van Riel
2018-09-18 15:29               ` Paolo Bonzini
2018-09-18 16:04                 ` Sebastian Andrzej Siewior
2018-09-18 17:29                   ` Rik van Riel
2018-09-19  5:55                     ` Paolo Bonzini
2018-09-19 16:57                       ` Sebastian Andrzej Siewior
2018-09-19 17:00                         ` Paolo Bonzini
2018-09-19 17:19                           ` Sebastian Andrzej Siewior
2018-09-19 19:38                           ` Rik van Riel
2018-09-19 19:49                           ` Andy Lutomirski
2018-09-12 15:20   ` [RFC PATCH 04/10] " Andy Lutomirski
2018-09-12 15:30     ` Rik van Riel
2018-09-12 15:49       ` Andy Lutomirski
2018-09-19 16:58         ` Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 05/10] x86/pkeys: Drop the preempt-disable section Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 06/10] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 07/10] x86/entry: add TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 08/10] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 09/10] x86/fpu: copy non-resident FPU state at fork time Sebastian Andrzej Siewior
2018-09-12 13:33 ` [RFC PATCH 10/10] x86/fpu: defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-09-12 15:47   ` Andy Lutomirski
2018-09-19 17:05     ` Sebastian Andrzej Siewior
2018-09-21  3:45       ` Andy Lutomirski
2018-09-21  4:15         ` Andy Lutomirski
2018-09-26 11:12           ` Sebastian Andrzej Siewior
2018-09-26 14:34             ` Andy Lutomirski
2018-09-26 15:32               ` Sebastian Andrzej Siewior
2018-09-26 16:24                 ` Andy Lutomirski

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