From: Manali Shukla Manali.Shukla@amd.com
The Idle HLT Intercept feature allows for the HLT instruction execution by a vCPU to be intercepted by the hypervisor only if there are no pending events (V_INTR and V_NMI) for the vCPU. When the vCPU is expected to service the pending events (V_INTR and V_NMI), the Idle HLT intercept won’t trigger. The feature allows the hypervisor to determine if the vCPU is idle and reduces wasteful VMEXITs.
In addition to the aforementioned use case, the Idle HLT intercept feature is also used for enlightened guests who aim to securely manage events without the hypervisor’s awareness. If a HLT occurs while a virtual event is pending and the hypervisor is unaware of this pending event (as could be the case with enlightened guests), the absence of the Idle HLT intercept feature could result in a vCPU being suspended indefinitely.
Presence of Idle HLT intercept feature for guests is indicated via CPUID function 0x8000000A_EDX[30].
Signed-off-by: Manali Shukla Manali.Shukla@amd.com Acked-by: Borislav Petkov (AMD) bp@alien8.de --- 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 645aa360628d..4fef0533f764 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -386,6 +386,7 @@ #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_IDLE_HLT (15*32+30) /* IDLE HLT intercept */
/* Intel-defined CPU features, CPUID level 0x00000007:0 (ECX), word 16 */ #define X86_FEATURE_AVX512VBMI (16*32+ 1) /* "avx512vbmi" AVX512 Vector Bit Manipulation instructions*/
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