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 16:05:14 +0200 |
| commit | 0029b3c1320bb9cf6ce1e9bf93dadd909ca06fa1 (patch) | |
| tree | 6c25246b79a1065c47c2abbee25364d85d17b901 | |
| parent | 331cfdd27429ed7a64923123b2482e85238979fa (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 | 25 | ||||
| -rw-r--r-- | arch/x86/kernel/process.c | 16 |
2 files changed, 27 insertions, 14 deletions
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index b409579f5261..7f9a97c572fe 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -44,8 +44,6 @@ static __always_inline void __monitorx(const void *eax, unsigned long ecx, static __always_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)); @@ -98,7 +96,6 @@ static __always_inline void __mwaitx(unsigned long eax, unsigned long ebx, */ static __always_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;" @@ -117,21 +114,29 @@ static __always_inline void __sti_mwait(unsigned long eax, unsigned long ecx) */ static __always_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()) { const void *addr = ¤t_thread_info()->flags; alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [addr] "a" (addr)); __monitor(addr, 0, 0); - if (!need_resched()) { - if (ecx & 1) { - __mwait(eax, ecx); - } else { - __sti_mwait(eax, ecx); - raw_local_irq_disable(); - } + if (need_resched()) + goto out; + + if (ecx & 1) { + __mwait(eax, ecx); + } else { + __sti_mwait(eax, ecx); + raw_local_irq_disable(); } } + +out: current_clr_polling(); } diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 1dbd7a34645c..4c9c98c5deab 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -911,16 +911,24 @@ static __init bool prefer_mwait_c1_over_halt(void) */ static __cpuidle void mwait_idle(void) { + if (need_resched()) + return; + + x86_idle_clear_cpu_buffers(); + if (!current_set_polling_and_test()) { const void *addr = ¤t_thread_info()->flags; alternative_input("", "clflush (%[addr])", X86_BUG_CLFLUSH_MONITOR, [addr] "a" (addr)); __monitor(addr, 0, 0); - if (!need_resched()) { - __sti_mwait(0, 0); - raw_local_irq_disable(); - } + if (need_resched()) + goto out; + + __sti_mwait(0, 0); + raw_local_irq_disable(); } + +out: __current_clr_polling(); } |