KVM: avoid fx_init() schedule in atomic

This make sure not to schedule in atomic during fx_init. I also
changed the name of fpu_init to fx_finit to avoid duplicating the name
with fpu_init that is already used in the kernel, this makes grep
simpler if nothing else.

Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 11 insertions, 2 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index bc224bba1e87..21338bdb28ff 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3703,10 +3703,19 @@ void fx_init(struct kvm_vcpu *vcpu)
 {
         unsigned after_mxcsr_mask;
 
+        /*
+         * Touch the fpu the first time in non atomic context as if
+         * this is the first fpu instruction the exception handler
+         * will fire before the instruction returns and it'll have to
+         * allocate ram with GFP_KERNEL.
+         */
+        if (!used_math())
+                fx_save(&vcpu->arch.host_fx_image);
+
         /* Initialize guest FPU by resetting ours and saving into guest's */
         preempt_disable();
         fx_save(&vcpu->arch.host_fx_image);
-        fpu_init();
+        fx_finit();
         fx_save(&vcpu->arch.guest_fx_image);
         fx_restore(&vcpu->arch.host_fx_image);
         preempt_enable();
diff --git a/include/asm-x86/kvm_host.h b/include/asm-x86/kvm_host.h
index 4baa9c9e1f41..1d8cd01fa514 100644
--- a/include/asm-x86/kvm_host.h
+++ b/include/asm-x86/kvm_host.h
@@ -627,7 +627,7 @@ static inline void fx_restore(struct i387_fxsave_struct *image)
         asm("fxrstor (%0)":: "r" (image));
 }
 
-static inline void fpu_init(void)
+static inline void fx_finit(void)
 {
         asm("finit");
 }