x86/fpu: Remove 'cpu' argument from __cpu_invalidate_fpregs_state()

The __{fpu,cpu}_invalidate_fpregs_state() functions can only be used
to invalidate a resource they control.  Document that, and change
the API a little bit to reflect that.

Go back to open coding the fpu_fpregs_owner_ctx write in the CPU
hotplug code, which should be the exception, and move __kernel_fpu_begin()
to this API.

This patch has no functional changes to the current code.

Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Dave Hansen <dave.hansen@intel.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>
Link: http://lkml.kernel.org/r/1476447331-21566-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 9 insertions, 8 deletions

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 1dcb29e8d92c..590f27488fca 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -488,15 +488,16 @@ DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
  *
  * Any code that clobbers the FPU registers or updates the in-memory
  * FPU state for a task MUST let the rest of the kernel know that the
- * FPU registers are no longer valid for this task. Calling either of
- * these two invalidate functions is enough, use whichever is convenient.
+ * FPU registers are no longer valid for this task.
  *
- * Must be run with preemption disabled: this clears the fpu_fpregs_owner_ctx,
- * on this CPU.
+ * Either one of these invalidation functions is enough. Invalidate
+ * a resource you control: CPU if using the CPU for something else
+ * (with preemption disabled), FPU for the current task, or a task that
+ * is prevented from running by the current task.
  */
-static inline void __cpu_invalidate_fpregs_state(unsigned int cpu)
+static inline void __cpu_invalidate_fpregs_state(void)
 {
-        per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;
+        __this_cpu_write(fpu_fpregs_owner_ctx, NULL);
 }
 
 static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 25a45ddfdbcf..30f11ab6c07e 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -106,7 +106,7 @@ void __kernel_fpu_begin(void)
                  */
                 copy_fpregs_to_fpstate(fpu);
         } else {
-                this_cpu_write(fpu_fpregs_owner_ctx, NULL);
+                __cpu_invalidate_fpregs_state();
         }
 }
 EXPORT_SYMBOL(__kernel_fpu_begin);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ca4c4ca2f6af..5cb801acc2e5 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1111,7 +1111,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
                 return err;
 
         /* the FPU context is blank, nobody can own it */
-        __cpu_invalidate_fpregs_state(cpu);
+        per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;
 
         common_cpu_up(cpu, tidle);