KVM: fx_init() needs preemption disabled while it plays with the FPU state

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

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 7aeaaba79c548fffaca68b6800faf3b0e187a529..5b42731beba41fd865235736172189468232b6b4 100644 (file)
--- 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;