linux-kernel - [PATCH 16/33] x86/fpu: Make the fpu state change in fpu_

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Date:   Sat, 23 Sep 2017 14:59:59 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Eric Biggers <ebiggers3@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH 16/33] x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic

Do this temporarily only, to make it easier to change the FPU state machine,
in particular this change couples the fpu->fpregs_active and fpu->fpstate_active
states: they are only set/cleared together (as far as the scheduler sees them).

This will be removed by later patches.

Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index bad57248e5a0..b7dc3833d41a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -462,9 +462,11 @@ void fpu__clear(struct fpu *fpu)
 	 * Make sure fpstate is cleared and initialized.
 	 */
 	if (static_cpu_has(X86_FEATURE_FPU)) {
+		preempt_disable();
 		fpu__activate_curr(fpu);
 		user_fpu_begin();
 		copy_init_fpstate_to_fpregs();
+		preempt_enable();
 	}
 }
 
-- 
2.11.0