linux-kernel - [PATCH 030/104] KVM: fx_init() needs preemption disabled while it plays with the FPU state

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Date:	Mon, 17 Sep 2007 10:31:12 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	kvm-devel@...ts.sourceforge.net
Cc:	linux-kernel@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH 030/104] KVM: fx_init() needs preemption disabled while it plays with the FPU state

From: Rusty Russell <rusty@...tcorp.com.au>

Now that kvm generally runs with preemption enabled, we need to protect
the fpu intialization sequence.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 drivers/kvm/kvm_main.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 7aeaaba..5b42731 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -693,10 +693,13 @@ void fx_init(struct kvm_vcpu *vcpu)
 
 	} *fx_image;
 
+	/* Initialize guest FPU by resetting ours and saving into guest's */
+	preempt_disable();
 	fx_save(vcpu->host_fx_image);
 	fpu_init();
 	fx_save(vcpu->guest_fx_image);
 	fx_restore(vcpu->host_fx_image);
+	preempt_enable();
 
 	fx_image = (struct fx_image_s *)vcpu->guest_fx_image;
 	fx_image->mxcsr = 0x1f80;
-- 
1.5.3

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