| Message ID | 20241004053341.5726-2-manali.shukla@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for the Bus Lock Threshold | expand |
On October 4, 2024 7:33:38 AM GMT+02:00, Manali Shukla <manali.shukla@amd.com> 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@amd.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 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?
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@amd.com> 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@amd.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 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@amd.com/T/#mb225b5b5fad2c070d4fadd51a076e9a05330b6a3 -Manali
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 */ /* Intel-defined CPU features, CPUID level 0x00000007:0 (ECX), word 16 */ #define X86_FEATURE_AVX512VBMI (16*32+ 1) /* "avx512vbmi" AVX512 Vector Bit Manipulation instructions*/
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@amd.com> --- arch/x86/include/asm/cpufeatures.h | 1 + 1 file changed, 1 insertion(+) base-commit: efbc6bd090f48ccf64f7a8dd5daea775821d57ec