6.15-stable review patch. If anyone has any objections, please let me know.
------------------
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 --- arch/x86/include/asm/mwait.h | 25 +++++++++++++++---------- arch/x86/kernel/process.c | 16 ++++++++++++---- 2 files changed, 27 insertions(+), 14 deletions(-)
--- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -43,8 +43,6 @@ static __always_inline void __monitorx(c
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)); @@ -97,7 +95,6 @@ static __always_inline void __mwaitx(uns */ 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;" @@ -116,21 +113,29 @@ static __always_inline void __sti_mwait( */ 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(); }
--- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -912,16 +912,24 @@ static __init bool prefer_mwait_c1_over_ */ 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(); }