From: Oleg Nesterov <oleg@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Rik van Riel <riel@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Suresh Siddha <sbsiddha@gmail.com>,
linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com,
matt.fleming@intel.com, bp@suse.de, pbonzini@redhat.com,
tglx@linutronix.de, luto@amacapital.net
Subject: Re: [PATCH 0/3] x86, fpu: more eagerfpu cleanups
Date: Fri, 20 Feb 2015 14:30:02 +0100 [thread overview]
Message-ID: <20150220133002.GA32275@redhat.com> (raw)
In-Reply-To: <20150220121009.GA19589@pd.tnic>
On 02/20, Borislav Petkov wrote:
>
> On Mon, Jan 19, 2015 at 07:51:09PM +0100, Oleg Nesterov wrote:
> > math_state_restore() and its usage doesn't look nice. init_fpu() too,
>
> Yeah, about that:
>
> I see:
>
> math_state_restore
> ...
> if (!tsk_used_math(tsk))
> init_fpu()
>
> and init_fpu() then does:
>
> if (tsk_used_math(tsk))
>
Yes, and more. math_state_restore() assumes that it is called with irqs
disabled. At least if !tsk_used_math. That is why 3/3 calls init_fpu()
first. Not only this doesn't look clean, this is simply not true in
general.
The comment above init_fpu() is simply wrong. And unlazy_fpu() from
there doesn't look nice. This mixes 2 completely differents things.
> Could use a cleanup and so on... Perhaps it is in the works already :)
Yes, I'll try to make the cleanups on top of these changes. And let me
repeat that there is another reason for 1/3 and 2/3 at least (3/3 makes
sense too), if we add TIF_LOAD_FPU we need to avoid the performance
regression (irq_fpu_usable() should not fail if !__thread_has_fpu()).
Oleg.
prev parent reply other threads:[~2015-02-20 13:32 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-11 21:46 [RFC PATCH 0/11 BROKEN] move FPU context loading to userspace switch riel
2015-01-11 21:46 ` [RFC PATCH 01/11] x86,fpu: document the data structures a little riel
2015-01-12 21:18 ` Borislav Petkov
2015-01-12 21:38 ` Rik van Riel
2015-01-12 21:52 ` Dave Hansen
2015-01-13 15:59 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 02/11] x86,fpu: replace fpu_switch_t with a thread flag riel
2015-01-13 15:24 ` Oleg Nesterov
2015-01-13 16:35 ` Rik van Riel
2015-01-13 16:55 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 03/11] x86,fpu: move __thread_fpu_begin to when the task has the fpu riel
2015-01-13 15:24 ` Oleg Nesterov
2015-01-13 16:37 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 04/11] x86,fpu: defer FPU restore until return to userspace riel
2015-01-13 15:53 ` Oleg Nesterov
2015-01-13 17:07 ` Andy Lutomirski
2015-01-13 17:11 ` Oleg Nesterov
2015-01-13 17:18 ` Andy Lutomirski
2015-01-13 17:44 ` Rik van Riel
2015-01-13 17:57 ` Andy Lutomirski
2015-01-13 18:13 ` Rik van Riel
2015-01-13 18:26 ` Andy Lutomirski
2015-01-13 17:54 ` Rik van Riel
2015-01-13 18:22 ` Oleg Nesterov
2015-01-13 18:30 ` Oleg Nesterov
2015-01-13 20:06 ` Rik van Riel
2015-01-14 17:56 ` Oleg Nesterov
2015-01-13 17:58 ` Oleg Nesterov
2015-01-13 19:32 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 05/11] x86,fpu: ensure FPU state is reloaded from memory if task is traced riel
2015-01-13 16:19 ` Oleg Nesterov
2015-01-13 16:33 ` Rik van Riel
2015-01-13 16:50 ` Oleg Nesterov
2015-01-13 16:57 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 06/11] x86,fpu: lazily skip fpu restore with eager fpu mode, too riel
2015-01-13 17:11 ` Andy Lutomirski
2015-01-13 20:43 ` Rik van Riel
2015-01-14 18:36 ` Oleg Nesterov
2015-01-15 2:49 ` Rik van Riel
2015-01-15 19:34 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 07/11] x86,fpu: store current fpu pointer, instead of fpu_owner_task riel
2015-01-11 21:46 ` [RFC PATCH 08/11] x86,fpu: restore user FPU state lazily after __kernel_fpu_end riel
2015-01-14 18:43 ` Oleg Nesterov
2015-01-14 19:08 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 09/11] x86,fpu,kvm: keep vcpu FPU active as long as it is resident riel
2015-01-11 21:46 ` [RFC PATCH 10/11] x86,fpu: fix fpu_copy to deal with not-loaded fpu riel
2015-01-11 21:46 ` [RFC PATCH 11/11] (BROKEN) x86,fpu: broken signal handler stack setup riel
2015-01-15 19:19 ` [PATCH 0/3] x86, fpu: kernel_fpu_begin/end initial cleanups/fix Oleg Nesterov
2015-01-15 19:19 ` [PATCH 1/3] x86, fpu: introduce per-cpu "bool in_kernel_fpu" Oleg Nesterov
2015-01-16 2:22 ` Rik van Riel
2015-01-20 12:54 ` [tip:x86/fpu] x86, fpu: Introduce per-cpu in_kernel_fpu state tip-bot for Oleg Nesterov
2015-01-15 19:20 ` [PATCH 2/3] x86, fpu: don't abuse ->has_fpu in __kernel_fpu_{begin,end}() Oleg Nesterov
2015-01-16 2:27 ` Rik van Riel
2015-01-16 15:54 ` Oleg Nesterov
2015-01-16 16:07 ` Rik van Riel
2015-01-20 12:55 ` [tip:x86/fpu] x86, fpu: Don't abuse has_fpu in __kernel_fpu_begin /end() tip-bot for Oleg Nesterov
2015-01-15 19:20 ` [PATCH 3/3] x86, fpu: fix math_state_restore() race with kernel_fpu_begin() Oleg Nesterov
2015-01-16 2:30 ` Rik van Riel
2015-01-16 16:03 ` Oleg Nesterov
2015-01-20 12:55 ` [tip:x86/fpu] x86, fpu: Fix " tip-bot for Oleg Nesterov
2015-01-19 18:51 ` [PATCH 0/3] x86, fpu: more eagerfpu cleanups Oleg Nesterov
2015-01-19 18:51 ` [PATCH 1/3] x86, fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu() Oleg Nesterov
2015-01-20 14:15 ` Rik van Riel
2015-02-20 18:13 ` Borislav Petkov
2015-03-03 11:27 ` [tip:x86/fpu] x86/fpu: " tip-bot for Oleg Nesterov
2015-01-19 18:51 ` [PATCH 2/3] x86, fpu: always allow FPU in interrupt " Oleg Nesterov
2015-01-20 14:46 ` Rik van Riel
2015-01-20 22:46 ` Andy Lutomirski
2015-02-20 21:48 ` Borislav Petkov
2015-03-03 11:28 ` [tip:x86/fpu] x86/fpu: Always " tip-bot for Oleg Nesterov
2015-01-19 18:52 ` [PATCH 3/3] x86, fpu: don't abuse FPU in kernel threads " Oleg Nesterov
2015-01-20 14:53 ` Rik van Riel
2015-02-23 15:31 ` Borislav Petkov
2015-03-03 11:28 ` [tip:x86/fpu] x86/fpu: Don' t " tip-bot for Oleg Nesterov
2015-02-20 12:10 ` [PATCH 0/3] x86, fpu: more eagerfpu cleanups Borislav Petkov
2015-02-20 13:30 ` Oleg Nesterov [this message]
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