x86/fpu: Split old & new FPU code paths

Now that CR0.TS is no longer being manipulated, we can simplify
switch_fpu_prepare() by no longer nesting the handling of new_fpu
inside the two branches for the old_fpu.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-10-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index d0324bc..1dcb29e 100644 (file)
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -581,23 +581,17 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
                /* But leave fpu_fpregs_owner_ctx! */
                old_fpu->fpregs_active = 0;
                trace_x86_fpu_regs_deactivated(old_fpu);
+       } else
+               old_fpu->last_cpu = -1;
 
-               /* Don't change CR0.TS if we just switch! */
-               if (fpu.preload) {
-                       fpregs_activate(new_fpu);
-                       trace_x86_fpu_regs_activated(new_fpu);
+       if (fpu.preload) {
+               if (fpregs_state_valid(new_fpu, cpu))
+                       fpu.preload = 0;
+               else
                        prefetch(&new_fpu->state);
-               }
-       } else {
-               old_fpu->last_cpu = -1;
-               if (fpu.preload) {
-                       if (fpregs_state_valid(new_fpu, cpu))
-                               fpu.preload = 0;
-                       else
-                               prefetch(&new_fpu->state);
-                       fpregs_activate(new_fpu);
-               }
+               fpregs_activate(new_fpu);
        }
+
        return fpu;
 }