fx_init schedule in atomic

Hello,

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.

index 578a0c1..5398b1c 100644
@@ -3701,10 +3702,19 @@ 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();

index 4baa9c9..b9a1421 100644
@@ -627,7 +635,7 @@ 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");
 }

-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2.
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone

Applied, thanks. Dynamic allocation for the fpu state was introduced in 2.6.26-rc, right?

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.


-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference 
Don't miss this year's exciting event. There's still time to save $100. 
Use priority code J8TL2D2. 
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone

It seems very recent, hit mainline on 30 Apr.

Also we may want to think if there's something cheaper than fx_save to trigger a math exception that doesn't alter the fpu state, I didn't think much about it given it's such a slow path that's probably not worth changing with something more complicated anyway. And bringing in a few l1 exclusive cachelines in the cpu should allow the second instruction to repeat faster than the first.

-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2.
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone

Oh, it's hardly performance critical. I think it is fine as is.

error compiling committee.c: too many arguments to function


-------------------------------------------------------------------------
This SF.net email is sponsored by the 2008 JavaOne(SM) Conference 
Don't miss this year's exciting event. There's still time to save $100. 
Use priority code J8TL2D2. 
http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone