commit c5bedc6847c3be6efe0e671a6155c9a25fd468bf
author Ingo Molnar <mingo@kernel.org> Thu Apr 23 12:49:20 2015 +0200
committer Ingo Molnar <mingo@kernel.org> Tue May 19 15:47:25 2015 +0200
tree f1eb66ea2807447c95e915f281d6815578b7e627
parent af7f8721f1f1252473b154c38dd7583abfe3206b

x86/fpu: Get rid of PF_USED_MATH usage, convert it to fpu->fpstate_active

Introduce a simple fpu->fpstate_active flag in the fpu context data structure
and use that instead of PF_USED_MATH in task->flags.

Testing for this flag byte should be slightly more efficient than
testing a bit in a bitmask, but the main advantage is that most
FPU functions can now be performed on a 'struct fpu' alone, they
don't need access to 'struct task_struct' anymore.

There's a slight linecount increase, mostly due to the 'fpu' local
variables and due to extra comments. The local variables will go away
once we move most of the FPU methods to pure 'struct fpu' parameters.

Reviewed-by: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kvm/x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0635a1f..bab8afb 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6597,10 +6597,11 @@
 
 int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
+	struct fpu *fpu = &current->thread.fpu;
 	int r;
 	sigset_t sigsaved;
 
-	if (!(current->flags & PF_USED_MATH) && fpstate_alloc_init(current))
+	if (!fpu->fpstate_active && fpstate_alloc_init(current))
 		return -ENOMEM;
 
 	if (vcpu->sigset_active)