From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
"Andy Lutomirski" <luto@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
"Rik van Riel" <riel@surriel.com>
Subject: Re: [PATCH 10/11] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU
Date: Fri, 2 Nov 2018 23:55:08 +0100 [thread overview]
Message-ID: <20181102225508.nv552gj356aykahf@linutronix.de> (raw)
In-Reply-To: <ef6012c0-52b9-14bb-c581-97627fdd5cb5@linux.intel.com>
On 2018-10-12 12:40:19 [-0700], Dave Hansen wrote:
> On 10/04/2018 07:05 AM, Sebastian Andrzej Siewior wrote:
> > From: Rik van Riel <riel@surriel.com>
> >
> > If TIF_LOAD_FPU is set, then the registers are saved (not loaded). In that case
> > we skip the saving part.
>
> This sentence hurts my brain.
>
> "If TIF_LOAD_FPU is set the registers are ... not loaded"
>
> I think that means that something could use some better naming.
>
> Should TIF_LOAD_FPU be TIF_NEED_FPU_LOAD, perhaps?
ARM has TIF_FOREIGN_FPSTATE which basically means that the current FP
stat does not belong to current().
Let me try to use TIF_NEED_FPU_LOAD and see how that works out.
> > Signed-off-by: Rik van Riel <riel@surriel.com>
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> > ---
> > arch/x86/kernel/fpu/signal.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
> > index c8f5ff58578ed..979dcd1ed82e0 100644
> > --- a/arch/x86/kernel/fpu/signal.c
> > +++ b/arch/x86/kernel/fpu/signal.c
> > @@ -155,13 +155,17 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
> > sizeof(struct user_i387_ia32_struct), NULL,
> > (struct _fpstate_32 __user *) buf) ? -1 : 1;
> >
> > - /* Update the thread's fxstate to save the fsave header. */
> > - if (ia32_fxstate) {
> > - copy_fxregs_to_kernel(fpu);
> > - } else {
> > - copy_fpregs_to_fpstate(fpu);
> > - fpregs_deactivate(fpu);
> > + __fpregs_changes_begin();
> > + if (!test_thread_flag(TIF_LOAD_FPU)) {
>
> This needs commenting, please.
>
> If we do not need to load the FPU at return to userspace, it means the
> state is in the the registers, not the buffer. So, update the buffer to
> match the registers.
okay. Let me add this then.
Sebastian
next prev parent reply other threads:[~2018-11-02 22:55 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-04 14:05 [PATCH 00/11 v3] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 01/11] x86/entry: remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-10-11 16:27 ` Borislav Petkov
2018-10-04 14:05 ` [PATCH 02/11] x86/fpu: add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 03/11] x86/fpu: make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2018-10-11 17:30 ` Christophe de Dinechin
2018-10-18 11:19 ` Sebastian Andrzej Siewior
2018-10-12 15:52 ` Dave Hansen
2018-10-18 11:17 ` Sebastian Andrzej Siewior
2018-10-18 11:21 ` Sebastian Andrzej Siewior
2018-10-17 10:01 ` Borislav Petkov
2018-10-18 11:48 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 04/11] x86/fpu: eager switch PKRU state Sebastian Andrzej Siewior
2018-10-12 17:51 ` Dave Hansen
2018-10-12 18:09 ` Andy Lutomirski
2018-10-12 19:44 ` Dave Hansen
2018-10-18 16:13 ` Sebastian Andrzej Siewior
2018-10-18 17:50 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 05/11] x86/fpu: set PKRU state for kernel threads Sebastian Andrzej Siewior
2018-10-12 17:54 ` Dave Hansen
2018-10-12 18:02 ` Andy Lutomirski
2018-10-18 16:26 ` Sebastian Andrzej Siewior
2018-10-18 16:48 ` Andy Lutomirski
2018-10-18 17:47 ` Dave Hansen
2018-10-18 18:25 ` Sebastian Andrzej Siewior
2018-10-18 20:46 ` Andy Lutomirski
2018-10-18 20:56 ` Dave Hansen
2018-10-18 21:24 ` Sebastian Andrzej Siewior
2018-10-18 21:58 ` Andy Lutomirski
2018-10-19 7:44 ` Paolo Bonzini
2018-10-19 16:59 ` Andy Lutomirski
2018-10-19 17:01 ` Dave Hansen
2018-10-19 17:37 ` Andy Lutomirski
2018-10-19 18:26 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 06/11] x86/pkeys: make init_pkru_value static Sebastian Andrzej Siewior
2018-10-12 17:55 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 07/11] x86/pkeys: Drop the preempt-disable section Sebastian Andrzej Siewior
2018-10-12 17:58 ` Dave Hansen
2018-10-12 18:07 ` Andy Lutomirski
2018-10-12 20:26 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 08/11] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-10-11 17:50 ` Christophe de Dinechin
2018-10-11 21:18 ` Andy Lutomirski
2018-10-12 18:15 ` Dave Hansen
2018-11-02 14:42 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 09/11] x86/entry: add TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 10/11] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-12 19:40 ` Dave Hansen
2018-10-15 15:24 ` Borislav Petkov
2018-11-02 15:44 ` Sebastian Andrzej Siewior
2018-11-02 22:55 ` Sebastian Andrzej Siewior [this message]
2018-10-04 14:05 ` [PATCH 11/11] x86/fpu: defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-10-04 16:14 ` Andy Lutomirski
2018-10-12 20:25 ` Sebastian Andrzej Siewior
2018-10-04 16:45 ` [PATCH 00/11 v3] x86: load FPU registers on return to userland Rik van Riel
2018-10-04 16:50 ` Andy Lutomirski
2018-10-05 11:55 ` Sebastian Andrzej Siewior
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