Evolution-X-Devices/kernel_xiaomi_garnet
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

x86/process: Move the buffer clearing before MONITOR

Browse Source 
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>
This commit is contained in:
Borislav Petkov
2025-07-15 14:37:49 +02:00
committed by Greg Kroah-Hartman
parent 6fea1a4e15
commit a8a08f1e51
2 changed files with 23 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
arch/x86/include/asm/mwait.h
View File

@@ -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 *)&current_thread_info()->flags, 0, 0);
if (!need_resched())
__mwait(eax, ecx);
if (need_resched())
goto out;
__mwait(eax, ecx);
}
out:
current_clr_polling();
}

15
arch/x86/kernel/process.c
View File

@@ -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 *)&current_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();
}