diff options
| author | Borislav Petkov (AMD) <bp@alien8.de> | 2025-04-14 15:33:19 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-10 15:57:51 +0200 |
| commit | 21953dde398d8e8fd9472ae7f66d32bebddbd648 (patch) | |
| tree | bb3f4d6d7c5e82c161e90040d3ef494dc0580fa3 | |
| parent | c334ae4a545a1b1ae8aff4e5eb741af2c7624cc7 (diff) | |
x86/process: Move the buffer clearing before MONITOR
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 81d82ca6291e..5ce91d5dfab0 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -836,6 +836,11 @@ 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 */ @@ -844,13 +849,17 @@ 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(); } |