Messages in this thread Patch in this message | | | From | Fenghua Yu <> | Subject | [PATCH v3 1/4] x86/cpufeatures: Enumerate #DB for bus lock detection | Date | Sat, 21 Nov 2020 02:36:21 +0000 |
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A bus lock is acquired though either split locked access to writeback (WB) memory or any locked access to non-WB memory. This is typically >1000 cycles slower than an atomic operation within a cache line. It also disrupts performance on other cores.
Some CPUs have ability to notify the kernel by an #DB trap after a user instruction acquires a bus lock and is executed. This allows the kernel to enforce user application throttling or mitigations.
The CPU feature flag to be shown in /proc/cpuinfo will be "bus_lock_detect".
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> --- arch/x86/include/asm/cpufeatures.h | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index dad350d42ecf..f375d9cb8123 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -352,6 +352,7 @@ #define X86_FEATURE_AVX512_VPOPCNTDQ (16*32+14) /* POPCNT for vectors of DW/QW */ #define X86_FEATURE_LA57 (16*32+16) /* 5-level page tables */ #define X86_FEATURE_RDPID (16*32+22) /* RDPID instruction */ +#define X86_FEATURE_BUS_LOCK_DETECT (16*32+24) /* Bus Lock detect */ #define X86_FEATURE_CLDEMOTE (16*32+25) /* CLDEMOTE instruction */ #define X86_FEATURE_MOVDIRI (16*32+27) /* MOVDIRI instruction */ #define X86_FEATURE_MOVDIR64B (16*32+28) /* MOVDIR64B instruction */ -- 2.29.2
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