linux-kernel - [PATCH 3/4] x86/fpu: use restore_init_xstate() instead of math_state

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Message-ID: <20150311173449.GE5032@redhat.com>
Date:	Wed, 11 Mar 2015 18:34:49 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Dave Hansen <dave.hansen@...el.com>, Borislav Petkov <bp@...e.de>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: [PATCH 3/4] x86/fpu: use restore_init_xstate() instead of
	math_state_restore() on kthread exec

Change flush_thread() to do user_fpu_begin() + restore_init_xstate()
and avoid math_state_restore().

Note: "TODO: cleanup this horror" is still valid. We do not need
init_fpu() at all, we only need fpu_alloc() + memset(0). But this needs
other changes, in particular user_fpu_begin() should set used_math().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/kernel/process.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index dd9a069..c396de2 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -142,7 +142,8 @@ void flush_thread(void)
 		/* kthread execs. TODO: cleanup this horror. */
 		if (WARN_ON(init_fpu(current)))
 			force_sig(SIGKILL, current);
-		math_state_restore();
+		user_fpu_begin();
+		restore_init_xstate();
 	}
 }
 
-- 
1.5.5.1


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