On 10/6/2024 11:56 AM, Borislav Petkov wrote: > On October 4, 2024 7:33:38 AM GMT+02:00, Manali Shukla <manali.shukla@xxxxxxx> wrote: >> Misbehaving guests can cause bus locks to degrade the performance of >> the system. The Bus Lock Threshold feature can be used to address this >> issue by providing capability to the hypervisor to limit guest's >> ability to generate bus lock, thereby preventing system slowdown due >> to performance penalities. >> >> When the Bus Lock Threshold feature is enabled, the processor checks >> the bus lock threshold count before executing the buslock and decides >> whether to trigger bus lock exit or not. >> >> The value of the bus lock threshold count '0' generates bus lock >> exits, and if the value is greater than '0', the bus lock is executed >> successfully and the bus lock threshold count is decremented. >> >> Presence of the Bus Lock threshold feature is indicated via CPUID >> function 0x8000000A_EDX[29]. >> >> Signed-off-by: Manali Shukla <manali.shukla@xxxxxxx> >> --- >> 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 dd4682857c12..77fa8e743ccc 100644 >> --- a/arch/x86/include/asm/cpufeatures.h >> +++ b/arch/x86/include/asm/cpufeatures.h >> @@ -382,6 +382,7 @@ >> #define X86_FEATURE_V_SPEC_CTRL (15*32+20) /* "v_spec_ctrl" Virtual SPEC_CTRL */ >> #define X86_FEATURE_VNMI (15*32+25) /* "vnmi" Virtual NMI */ >> #define X86_FEATURE_SVME_ADDR_CHK (15*32+28) /* SVME addr check */ >> +#define X86_FEATURE_BUS_LOCK_THRESHOLD (15*32+29) /* "buslock" Bus lock threshold */ > > Why does this feature flag need to be visible in /proc/cpuinfo? > > This was already discussed on [v1] of the same series but never concluded. As suggested in the discussion [v1], I have added "buslock" to be enumerated in "/proc/cpuinfo". I really don't have any strong opinions about adding or removing it from "/proc/cpuinfo". So, I would let maintainers decide how to go about it. v1: https://lore.kernel.org/kvm/76355a11-a0ba-4a28-bf51-454facfd59e5@xxxxxxx/T/#mb225b5b5fad2c070d4fadd51a076e9a05330b6a3 -Manali
