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    SubjectRe: [PATCH v2 09/11] KVM: SVM: Add VNMI bit definition
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    On 2/1/2023 4:12 AM, Sean Christopherson wrote:
    > On Tue, Nov 29, 2022, Maxim Levitsky wrote:
    >> From: Santosh Shukla <santosh.shukla@amd.com>
    >>
    >> VNMI exposes 3 capability bits (V_NMI, V_NMI_MASK, and V_NMI_ENABLE) to
    >> virtualize NMI and NMI_MASK, Those capability bits are part of
    >> VMCB::intr_ctrl -
    >> V_NMI(11) - Indicates whether a virtual NMI is pending in the guest.
    >> V_NMI_MASK(12) - Indicates whether virtual NMI is masked in the guest.
    >> V_NMI_ENABLE(26) - Enables the NMI virtualization feature for the guest.
    >>
    >> When Hypervisor wants to inject NMI, it will set V_NMI bit, Processor
    >> will clear the V_NMI bit and Set the V_NMI_MASK which means the Guest is
    >> handling NMI, After the guest handled the NMI, The processor will clear
    >> the V_NMI_MASK on the successful completion of IRET instruction Or if
    >> VMEXIT occurs while delivering the virtual NMI.
    >>
    >> To enable the VNMI capability, Hypervisor need to program
    >> V_NMI_ENABLE bit 1.
    >>
    >> Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
    >> Signed-off-by: Santosh Shukla <santosh.shukla@amd.com>
    >> ---
    >> arch/x86/include/asm/svm.h | 7 +++++++
    >> 1 file changed, 7 insertions(+)
    >>
    >> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
    >> index cb1ee53ad3b189..26d6f549ce2b46 100644
    >> --- a/arch/x86/include/asm/svm.h
    >> +++ b/arch/x86/include/asm/svm.h
    >> @@ -203,6 +203,13 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
    >> #define X2APIC_MODE_SHIFT 30
    >> #define X2APIC_MODE_MASK (1 << X2APIC_MODE_SHIFT)
    >>
    >> +#define V_NMI_PENDING_SHIFT 11
    >> +#define V_NMI_PENDING (1 << V_NMI_PENDING_SHIFT)
    >> +#define V_NMI_MASK_SHIFT 12
    >> +#define V_NMI_MASK (1 << V_NMI_MASK_SHIFT)
    >
    > Argh, more KVM warts. The existing INT_CTL defines all use "mask" in the name,
    > so looking at V_NMI_MASK in the context of other code reads "vNMI is pending",
    > not "vNMIs are blocked".
    >
    > IMO, the existing _MASK terminology is the one that's wrong, but there's an absurd
    > amount of prior art in svm.h :-(
    >
    > And the really annoying one is V_INTR_MASKING_MASK, which IIRC says "virtual INTR
    > masking is enabled", not "virtual INTRs are blocked".
    >
    > So maybe call this V_NMI_BLOCKING_MASK? And tack on _MASK too the others (even
    > though I agree it's ugly).
    >

    Sure.

    >> +#define V_NMI_ENABLE_SHIFT 26
    >> +#define V_NMI_ENABLE (1 << V_NMI_ENABLE_SHIFT)
    >
    > Hrm. I think I would prefer to keep the defines ordered by bit position. Knowing
    > that there's an enable bit isn't all that critical for understanding vNMI pending
    > and blocked.

    Sure, Sean will include in V3.

    Thanks,
    Santosh

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