linux-kernel - [RFC PATCH 03/10] x86/fpu: add (__)make_fpregs

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Message-Id: <20180912133353.20595-4-bigeasy@linutronix.de>
Date:   Wed, 12 Sep 2018 15:33:46 +0200
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>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [RFC PATCH 03/10] 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/internal.h | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index a38bf5a1e37ad..16c4077ffc945 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -514,6 +514,26 @@ static inline void fpregs_activate(struct fpu *fpu)
 	trace_x86_fpu_regs_activated(fpu);
 }
 
+/*
+ * Load the FPU state for the current task. Call with preemption disabled.
+ */
+static inline void __fpregs_load_activate(struct fpu *fpu, int cpu)
+{
+	if (!fpregs_state_valid(fpu, cpu))
+		copy_kernel_to_fpregs(&fpu->state);
+	fpregs_activate(fpu);
+}
+
+static inline void __fpregs_changes_begin(void)
+{
+	preempt_disable();
+}
+
+static inline void __fpregs_changes_end(void)
+{
+	preempt_enable();
+}
+
 /*
  * FPU state switching for scheduling.
  *
@@ -553,11 +573,8 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 	bool preload = static_cpu_has(X86_FEATURE_FPU) &&
 		       new_fpu->initialized;
 
-	if (preload) {
-		if (!fpregs_state_valid(new_fpu, cpu))
-			copy_kernel_to_fpregs(&new_fpu->state);
-		fpregs_activate(new_fpu);
-	}
+	if (preload)
+		__fpregs_load_activate(new_fpu, cpu);
 }
 
 /*
-- 
2.19.0