| Message ID | 20241022054810.23369-2-manali.shukla@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for the Idle HLT intercept feature | expand |
On Tue, Oct 22, 2024 at 05:48:07AM +0000, Manali Shukla wrote: > 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 dd4682857c12..7461a49e1045 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_IDLE_HLT (15*32+30) /* "" IDLE HLT intercept */ Whoever commits this, you can remove the "" in the comment now as they're not needed anymore. Thx.
On Tue, Oct 22, 2024, Borislav Petkov wrote: > On Tue, Oct 22, 2024 at 05:48:07AM +0000, Manali Shukla wrote: > > 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 dd4682857c12..7461a49e1045 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_IDLE_HLT (15*32+30) /* "" IDLE HLT intercept */ > > Whoever commits this, you can remove the "" in the comment now as they're not > needed anymore. Ya, will do.
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index dd4682857c12..7461a49e1045 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_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*/