linux-kernel - [PATCH 09/22] x86/fpu: Add (__)make_fpregs

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Date:   Thu, 21 Feb 2019 12:50:07 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 09/22] x86/fpu: Add (__)make_fpregs_active helpers

From: Rik van Riel <riel@...riel.com>

Add helper function that ensures the floating point registers for
the current task are active. Use with preemption disabled.

Signed-off-by: Rik van Riel <riel@...riel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 arch/x86/include/asm/fpu/api.h      | 11 +++++++++++
 arch/x86/include/asm/fpu/internal.h | 19 +++++++++++--------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index b56d504af6545..73e684160f354 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -10,6 +10,7 @@
 
 #ifndef _ASM_X86_FPU_API_H
 #define _ASM_X86_FPU_API_H
+#include <linux/preempt.h>
 
 /*
  * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
@@ -22,6 +23,16 @@ extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
 
+static inline void fpregs_lock(void)
+{
+	preempt_disable();
+}
+
+static inline void fpregs_unlock(void)
+{
+	preempt_enable();
+}
+
 /*
  * Query the presence of one or more xfeatures. Works on any legacy CPU as well.
  *
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 96835d04e9343..67e4805bccb6f 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -515,6 +515,15 @@ static inline void fpregs_activate(struct fpu *fpu)
 	trace_x86_fpu_regs_activated(fpu);
 }
 
+static inline void __fpregs_load_activate(struct fpu *fpu, int cpu)
+{
+	if (!fpregs_state_valid(fpu, cpu)) {
+		if (current->mm)
+			copy_kernel_to_fpregs(&fpu->state);
+		fpregs_activate(fpu);
+	}
+}
+
 /*
  * FPU state switching for scheduling.
  *
@@ -553,14 +562,8 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
  */
 static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 {
-	if (static_cpu_has(X86_FEATURE_FPU)) {
-		if (!fpregs_state_valid(new_fpu, cpu)) {
-			if (current->mm)
-				copy_kernel_to_fpregs(&new_fpu->state);
-		}
-
-		fpregs_activate(new_fpu);
-	}
+	if (static_cpu_has(X86_FEATURE_FPU))
+		__fpregs_load_activate(new_fpu, cpu);
 }
 
 /*
-- 
2.20.1