From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org
Subject: [GIT pull] x86/fpu for v5.11-rc1
Date: Mon, 14 Dec 2020 20:22:21 -0000 [thread overview]
Message-ID: <160797734154.10793.1671535872493484817.tglx@nanos> (raw)
In-Reply-To: 160797732939.10793.9152151866806316627.tglx@nanos
Linus,
please pull the latest x86/fpu branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-fpu-2020-12-14
up to: cba08c5dc6dc: x86/fpu: Make kernel FPU protection RT friendly
X86 FPU updates:
- Simplify the FPU protection for !RT kernels
- Add the RT variant of FPU protections
Thanks,
tglx
------------------>
Thomas Gleixner (2):
x86/fpu: Simplify fpregs_[un]lock()
x86/fpu: Make kernel FPU protection RT friendly
arch/x86/include/asm/fpu/api.h | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index dcd9503b1098..a5aba4ab0224 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -29,17 +29,32 @@ extern void fpregs_mark_activate(void);
* A context switch will (and softirq might) save CPU's FPU registers to
* 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)
{
- preempt_disable();
- local_bh_disable();
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_disable();
+ else
+ preempt_disable();
}
static inline void fpregs_unlock(void)
{
- local_bh_enable();
- preempt_enable();
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_enable();
+ else
+ preempt_enable();
}
#ifdef CONFIG_X86_DEBUG_FPU
next prev parent reply other threads:[~2020-12-14 20:39 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-14 20:22 [GIT pull] core/entry for v5.11-rc1 Thomas Gleixner
2020-12-14 20:22 ` [GIT pull] core/rcu " Thomas Gleixner
2020-12-15 2:21 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] efi/core " Thomas Gleixner
2020-12-14 20:30 ` Thomas Gleixner
2020-12-24 21:59 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] irq/core " Thomas Gleixner
2020-12-15 2:02 ` Linus Torvalds
2020-12-15 14:19 ` Thomas Gleixner
2020-12-15 14:36 ` [GIT pull V2] " Thomas Gleixner
2020-12-16 1:00 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] locking/core " Thomas Gleixner
2020-12-15 2:21 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] perf/core " Thomas Gleixner
2020-12-15 2:21 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] perf/kprobes " Thomas Gleixner
2020-12-15 2:21 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] sched/core " Thomas Gleixner
2020-12-15 2:47 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] timers/core " Thomas Gleixner
2020-12-15 2:47 ` pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] x86/apic " Thomas Gleixner
2020-12-15 3:07 ` pr-tracker-bot
2020-12-14 20:22 ` Thomas Gleixner [this message]
2020-12-15 3:07 ` [GIT pull] x86/fpu " pr-tracker-bot
2020-12-14 20:22 ` [GIT pull] core/mm " Thomas Gleixner
2020-12-15 2:47 ` pr-tracker-bot
2020-12-15 2:21 ` [GIT pull] core/entry " pr-tracker-bot
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