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    SubjectRe: [RFC PATCH v5 039/104] KVM: x86/mmu: Disallow fast page fault on private GPA
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    On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
    > From: Isaku Yamahata <isaku.yamahata@intel.com>
    >
    > TDX requires TDX SEAMCALL to operate Secure EPT instead of direct memory
    > access and TDX SEAMCALL is heavy operation. Fast page fault on private GPA
    > doesn't make sense. Disallow fast page fault on private GPA.
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > ---
    > arch/x86/kvm/mmu/mmu.c | 7 +++++++
    > 1 file changed, 7 insertions(+)
    >
    > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
    > index e9212394a530..d8c1505155b0 100644
    > --- a/arch/x86/kvm/mmu/mmu.c
    > +++ b/arch/x86/kvm/mmu/mmu.c
    > @@ -3185,6 +3185,13 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
    > u64 *sptep = NULL;
    > uint retry_count = 0;
    >
    > + /*
    > + * TDX private mapping doesn't support fast page fault because the EPT
    > + * entry needs TDX SEAMCALL. not direct memory access.

    "the EPT entry is read/written with TDX SEAMCALLs instead of direct
    memory access".

    Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

    > + */
    > + if (kvm_is_private_gpa(vcpu->kvm, fault->addr))
    > + return ret;
    > +
    > if (!page_fault_can_be_fast(fault))
    > return ret;
    >

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