On Fri, May 02, 2025 at 05:03:43AM +0000, Manali Shukla 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 e95a8e9ef22b..b51f3ce84032 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -378,6 +378,7 @@
> #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) /* Bus lock threshold */
> #define X86_FEATURE_IDLE_HLT (15*32+30) /* IDLE HLT intercept */
>
> /* Intel-defined CPU features, CPUID level 0x00000007:0 (ECX), word 16 */
> --
Reviewed-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
