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From: Valentin Schneider <valentin.schneider@arm.com>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rt-users@vger.kernel.org, x86@kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>, Mark Brown <broonie@kernel.org>,
	Dave Martin <Dave.Martin@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH 2/3] x86/fpu: Make FPU protection reuse common helper
Date: Thu, 22 Jul 2021 18:51:56 +0100	[thread overview]
Message-ID: <20210722175157.1367122-3-valentin.schneider@arm.com> (raw)
In-Reply-To: <20210722175157.1367122-1-valentin.schneider@arm.com>

The newly-introduced preempt_{enable, disable}_bh() helpers are an exact
stand-in for fpregs_{lock, unlock}(). Use them there.

No change in behaviour intended.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
 arch/x86/include/asm/fpu/api.h | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index 62cf3e4c06fb..ffebb9316bfd 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -54,31 +54,16 @@ static inline void kernel_fpu_begin(void)
  * fpu->state and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in
  * a random state.
  *
- * local_bh_disable() protects against both preemption and soft interrupts
- * on !RT kernels.
- *
- * On RT kernels local_bh_disable() is not sufficient because it only
- * serializes soft interrupt related sections via a local lock, but stays
- * preemptible. Disabling preemption is the right choice here as bottom
- * half processing is always in thread context on RT kernels so it
- * implicitly prevents bottom half processing as well.
- *
  * Disabling preemption also serializes against kernel_fpu_begin().
  */
 static inline void fpregs_lock(void)
 {
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
-		local_bh_disable();
-	else
-		preempt_disable();
+	preempt_disable_bh();
 }
 
 static inline void fpregs_unlock(void)
 {
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
-		local_bh_enable();
-	else
-		preempt_enable();
+	preempt_enable_bh();
 }
 
 #ifdef CONFIG_X86_DEBUG_FPU
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <valentin.schneider@arm.com>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rt-users@vger.kernel.org, x86@kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>, Mark Brown <broonie@kernel.org>,
	Dave Martin <Dave.Martin@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: [PATCH 2/3] x86/fpu: Make FPU protection reuse common helper
Date: Thu, 22 Jul 2021 18:51:56 +0100	[thread overview]
Message-ID: <20210722175157.1367122-3-valentin.schneider@arm.com> (raw)
In-Reply-To: <20210722175157.1367122-1-valentin.schneider@arm.com>

The newly-introduced preempt_{enable, disable}_bh() helpers are an exact
stand-in for fpregs_{lock, unlock}(). Use them there.

No change in behaviour intended.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
 arch/x86/include/asm/fpu/api.h | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index 62cf3e4c06fb..ffebb9316bfd 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -54,31 +54,16 @@ static inline void kernel_fpu_begin(void)
  * fpu->state and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in
  * a random state.
  *
- * local_bh_disable() protects against both preemption and soft interrupts
- * on !RT kernels.
- *
- * On RT kernels local_bh_disable() is not sufficient because it only
- * serializes soft interrupt related sections via a local lock, but stays
- * preemptible. Disabling preemption is the right choice here as bottom
- * half processing is always in thread context on RT kernels so it
- * implicitly prevents bottom half processing as well.
- *
  * Disabling preemption also serializes against kernel_fpu_begin().
  */
 static inline void fpregs_lock(void)
 {
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
-		local_bh_disable();
-	else
-		preempt_disable();
+	preempt_disable_bh();
 }
 
 static inline void fpregs_unlock(void)
 {
-	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
-		local_bh_enable();
-	else
-		preempt_enable();
+	preempt_enable_bh();
 }
 
 #ifdef CONFIG_X86_DEBUG_FPU
-- 
2.25.1


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  parent reply	other threads:[~2021-07-22 17:53 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-22 17:51 [PATCH 0/3] sched, x86, arm64: PREEMPT_RT, FPU and preemption Valentin Schneider
2021-07-22 17:51 ` Valentin Schneider
2021-07-22 17:51 ` [PATCH 1/3] sched/preempt: Introduce preempt_{enable, disable}_bh() Valentin Schneider
2021-07-22 17:51   ` Valentin Schneider
2021-07-22 17:51 ` Valentin Schneider [this message]
2021-07-22 17:51   ` [PATCH 2/3] x86/fpu: Make FPU protection reuse common helper Valentin Schneider
2021-07-22 17:51 ` [PATCH 3/3] arm64/fpsimd: Fix FPSIMD context handling vs PREEMPT_RT Valentin Schneider
2021-07-22 17:51   ` Valentin Schneider
2021-07-22 18:32   ` Mark Brown
2021-07-22 18:32     ` Mark Brown
2021-07-23 11:07     ` Valentin Schneider
2021-07-23 11:07       ` Valentin Schneider
2021-07-22 20:11 ` [PATCH 0/3] sched, x86, arm64: PREEMPT_RT, FPU and preemption Andrew Halaney
2021-07-22 20:11   ` Andrew Halaney
2021-07-23 14:12 ` Ard Biesheuvel
2021-07-23 14:12   ` Ard Biesheuvel

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