* [PATCH] x86/traps: Have read_cr0() only once in the #NM handler
@ 2019-01-17 12:07 Borislav Petkov
2019-01-17 12:14 ` Sebastian Andrzej Siewior
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Borislav Petkov @ 2019-01-17 12:07 UTC (permalink / raw)
To: X86 ML; +Cc: LKML, Andy Lutomirski, Sebastian Andrzej Siewior
From: Borislav Petkov <bp@suse.de>
... instead of twice in the code. In any case, CR0 ends up being read
once anyway:
1. The CONFIG_MATH_EMULATION case does so and exits.
2. The normal case does it once too.
However, read it on function entry instead to make the code even simpler
to follow.
No functional changes.
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/kernel/traps.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a7..2684a9d11e66 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -880,12 +880,12 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
dotraplinkage void
do_device_not_available(struct pt_regs *regs, long error_code)
{
- unsigned long cr0;
+ unsigned long cr0 = read_cr0();
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
#ifdef CONFIG_MATH_EMULATION
- if (!boot_cpu_has(X86_FEATURE_FPU) && (read_cr0() & X86_CR0_EM)) {
+ if (!boot_cpu_has(X86_FEATURE_FPU) && (cr0 & X86_CR0_EM)) {
struct math_emu_info info = { };
cond_local_irq_enable(regs);
@@ -897,7 +897,6 @@ do_device_not_available(struct pt_regs *regs, long error_code)
#endif
/* This should not happen. */
- cr0 = read_cr0();
if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) {
/* Try to fix it up and carry on. */
write_cr0(cr0 & ~X86_CR0_TS);
--
2.19.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] x86/traps: Have read_cr0() only once in the #NM handler
2019-01-17 12:07 [PATCH] x86/traps: Have read_cr0() only once in the #NM handler Borislav Petkov
@ 2019-01-17 12:14 ` Sebastian Andrzej Siewior
2019-01-17 19:24 ` Andy Lutomirski
2019-01-22 13:30 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
2 siblings, 0 replies; 4+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-01-17 12:14 UTC (permalink / raw)
To: Borislav Petkov; +Cc: X86 ML, LKML, Andy Lutomirski
On 2019-01-17 13:07:28 [+0100], Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
>
> ... instead of twice in the code. In any case, CR0 ends up being read
> once anyway:
>
> 1. The CONFIG_MATH_EMULATION case does so and exits.
> 2. The normal case does it once too.
>
> However, read it on function entry instead to make the code even simpler
> to follow.
makes sense.
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Sebastian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] x86/traps: Have read_cr0() only once in the #NM handler
2019-01-17 12:07 [PATCH] x86/traps: Have read_cr0() only once in the #NM handler Borislav Petkov
2019-01-17 12:14 ` Sebastian Andrzej Siewior
@ 2019-01-17 19:24 ` Andy Lutomirski
2019-01-22 13:30 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
2 siblings, 0 replies; 4+ messages in thread
From: Andy Lutomirski @ 2019-01-17 19:24 UTC (permalink / raw)
To: Borislav Petkov; +Cc: X86 ML, LKML, Sebastian Andrzej Siewior
On Thu, Jan 17, 2019 at 4:07 AM Borislav Petkov <bp@alien8.de> wrote:
>
> From: Borislav Petkov <bp@suse.de>
>
> ... instead of twice in the code. In any case, CR0 ends up being read
> once anyway:
>
> 1. The CONFIG_MATH_EMULATION case does so and exits.
> 2. The normal case does it once too.
>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [tip:x86/fpu] x86/traps: Have read_cr0() only once in the #NM handler
2019-01-17 12:07 [PATCH] x86/traps: Have read_cr0() only once in the #NM handler Borislav Petkov
2019-01-17 12:14 ` Sebastian Andrzej Siewior
2019-01-17 19:24 ` Andy Lutomirski
@ 2019-01-22 13:30 ` tip-bot for Borislav Petkov
2 siblings, 0 replies; 4+ messages in thread
From: tip-bot for Borislav Petkov @ 2019-01-22 13:30 UTC (permalink / raw)
To: linux-tip-commits; +Cc: tglx, luto, hpa, linux-kernel, bigeasy, bp, mingo
Commit-ID: ee35b9b9f6d52ba134b4e75442531935f295be7a
Gitweb: https://git.kernel.org/tip/ee35b9b9f6d52ba134b4e75442531935f295be7a
Author: Borislav Petkov <bp@suse.de>
AuthorDate: Thu, 17 Jan 2019 13:02:05 +0100
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Tue, 22 Jan 2019 14:13:35 +0100
x86/traps: Have read_cr0() only once in the #NM handler
... instead of twice in the code. In any case, CR0 ends up being read
once anyway:
1. The CONFIG_MATH_EMULATION case does so and exits.
2. The normal case does it once too.
However, read it on function entry instead to make the code even simpler
to follow.
No functional changes.
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: x86@kernel.org
Link: https://lkml.kernel.org/r/20190117120728.3811-1-bp@alien8.de
---
arch/x86/kernel/traps.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a7..2684a9d11e66 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -880,12 +880,12 @@ do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
dotraplinkage void
do_device_not_available(struct pt_regs *regs, long error_code)
{
- unsigned long cr0;
+ unsigned long cr0 = read_cr0();
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
#ifdef CONFIG_MATH_EMULATION
- if (!boot_cpu_has(X86_FEATURE_FPU) && (read_cr0() & X86_CR0_EM)) {
+ if (!boot_cpu_has(X86_FEATURE_FPU) && (cr0 & X86_CR0_EM)) {
struct math_emu_info info = { };
cond_local_irq_enable(regs);
@@ -897,7 +897,6 @@ do_device_not_available(struct pt_regs *regs, long error_code)
#endif
/* This should not happen. */
- cr0 = read_cr0();
if (WARN(cr0 & X86_CR0_TS, "CR0.TS was set")) {
/* Try to fix it up and carry on. */
write_cr0(cr0 & ~X86_CR0_TS);
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-01-22 13:31 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2019-01-17 12:07 [PATCH] x86/traps: Have read_cr0() only once in the #NM handler Borislav Petkov
2019-01-17 12:14 ` Sebastian Andrzej Siewior
2019-01-17 19:24 ` Andy Lutomirski
2019-01-22 13:30 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
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