diff options
| author | Borislav Petkov <bp@kernel.org> | 2025-07-15 14:37:49 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-17 18:28:01 +0200 |
| commit | a8a08f1e519b4fd08adce08ebfa1763950be5d99 (patch) | |
| tree | e51bd19a42a4d53d7ad9e8c5e2d99b9da8018863 | |
| parent | 6fea1a4e150f1fe3726310558f33a30e0c209153 (diff) | |
x86/process: Move the buffer clearing before MONITOR
From: "Borislav Petkov (AMD)" <bp@alien8.de>
Commit 8e786a85c0a3c0fffae6244733fb576eeabd9dec upstream.
Move the VERW clearing before the MONITOR so that VERW doesn't disarm it
and the machine never enters C1.
Original idea by Kim Phillips <kim.phillips@amd.com>.
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/include/asm/mwait.h | 16 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 15 |
2 files changed, 23 insertions, 8 deletions
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index 20b33e6370c3..2a2de4f3cb20 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -43,8 +43,6 @@ static inline void __monitorx(const void *eax, unsigned long ecx, static inline void __mwait(unsigned long eax, unsigned long ecx) { - x86_idle_clear_cpu_buffers(); - /* "mwait %eax, %ecx;" */ asm volatile(".byte 0x0f, 0x01, 0xc9;" :: "a" (eax), "c" (ecx)); @@ -88,7 +86,6 @@ static inline void __mwaitx(unsigned long eax, unsigned long ebx, static inline void __sti_mwait(unsigned long eax, unsigned long ecx) { - x86_idle_clear_cpu_buffers(); /* "mwait %eax, %ecx;" */ asm volatile("sti; .byte 0x0f, 0x01, 0xc9;" @@ -107,6 +104,11 @@ static inline void __sti_mwait(unsigned long eax, unsigned long ecx) */ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) { + if (need_resched()) + return; + + x86_idle_clear_cpu_buffers(); + if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test()) { if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) { mb(); @@ -115,9 +117,13 @@ static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) } __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __mwait(eax, ecx); + if (need_resched()) + goto out; + + __mwait(eax, ecx); } + +out: current_clr_polling(); } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 34e7c49b8057..fd91c301218d 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -825,6 +825,11 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c) */ static __cpuidle void mwait_idle(void) { + if (need_resched()) + return; + + x86_idle_clear_cpu_buffers(); + if (!current_set_polling_and_test()) { if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) { mb(); /* quirk */ @@ -833,13 +838,17 @@ static __cpuidle void mwait_idle(void) } __monitor((void *)¤t_thread_info()->flags, 0, 0); - if (!need_resched()) - __sti_mwait(0, 0); - else + if (need_resched()) { raw_local_irq_enable(); + goto out; + } + + __sti_mwait(0, 0); } else { raw_local_irq_enable(); } + +out: __current_clr_polling(); } |