The following commit has been merged into the x86/splitlock branch of tip: Commit-ID: f21d4d3b97a8603567e5d4250bd75e8ebbd520af Gitweb: https://git.kernel.org/tip/f21d4d3b97a8603567e5d4250bd75e8ebbd520af Author: Fenghua Yu <fenghua...@intel.com> AuthorDate: Mon, 22 Mar 2021 13:53:23 Committer: Thomas Gleixner <t...@linutronix.de> CommitterDate: Sun, 28 Mar 2021 22:52:14 +02:00
x86/cpufeatures: Enumerate #DB for bus lock detection A bus lock is acquired through either a 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 the ability to notify the kernel by a #DB trap after a user instruction acquires a bus lock and is executed. This allows the kernel to enforce user application throttling or mitigation. Both breakpoint and bus lock can trigger the #DB trap in the same instruction and the ordering of handling them is the kernel #DB handler's choice. The CPU feature flag to be shown in /proc/cpuinfo will be "bus_lock_detect". Signed-off-by: Fenghua Yu <fenghua...@intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Tony Luck <tony.l...@intel.com> Link: https://lore.kernel.org/r/20210322135325.682257-2-fenghua...@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 cc96e26..faec3d9 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -354,6 +354,7 @@ #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 */
