On Wed, Sep 21, 2022, Vitaly Kuznetsov wrote: > diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h > index 7ad56fbc4b4d..dd1589336e79 100644 > --- a/arch/x86/kvm/vmx/evmcs.h > +++ b/arch/x86/kvm/vmx/evmcs.h > @@ -63,6 +63,15 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs); > #define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (0) > #define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING) > > +/* > + * Note, Hyper-V isn't actually stealing bit 28 from Intel, just abusing it by > + * pairing it with architecturally impossible exit reasons. Bit 28 is set only > + * on SMI exits to a SMI transfer monitor (STM) and if and only if a MTF VM-Exit > + * is pending. I.e. it will never be set by hardware for non-SMI exits (there > + * are only three), nor will it ever be set unless the VMM is an STM. > + */ > +#define HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH 0x10000031 This definition should go into hyperv-tlfs.h since it's take verbatim from the TLFS. https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/nested-virtualization#synthetic-vm-exit
