linux-kernel - [PATCH 4/5] x86-64: move unlazy_fpu() into lazy cpu state part of context switch

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Date:	Thu, 11 Jun 2009 12:20:39 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Alok Kataria <akataria@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH 4/5] x86-64: move unlazy_fpu() into lazy cpu state part of context switch

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

Make sure that unlazy_fpu()'s stts gets batched along with the other
cpu state changes during context switch.  (32-bit already does this.)

This makes sure it gets batched when running paravirtualized.

[ Impact: optimise paravirtual FPU context switch ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Cc: Alok Kataria <akataria@...are.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>
---
 arch/x86/kernel/process_64.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 89c46f1..6ed1c57 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -432,6 +432,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	load_TLS(next, cpu);
 
+	/* Must be after DS reload */
+	unlazy_fpu(prev_p);
+
 	/*
 	 * Leave lazy mode, flushing any hypercalls made here.
 	 * This must be done before restoring TLS segments so
@@ -472,9 +475,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 		wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
 	prev->gsindex = gsindex;
 
-	/* Must be after DS reload */
-	unlazy_fpu(prev_p);
-
 	/*
 	 * Switch the PDA and FPU contexts.
 	 */
-- 
1.6.2.2

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