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    SubjectRe: [PATCH v2 1/6] KVM: x86/mmu: Fix wrong gfn range of tlb flushing in validate_direct_spte()
    On Tue, 13 Sept 2022 at 20:13, Hou Wenlong <houwenlong.hwl@antgroup.com> wrote:
    >
    > On Thu, Sep 08, 2022 at 01:43:54AM +0800, David Matlack wrote:
    > > On Wed, Aug 24, 2022 at 05:29:18PM +0800, Hou Wenlong wrote:
    > > > The spte pointing to the children SP is dropped, so the
    > > > whole gfn range covered by the children SP should be flushed.
    > > > Although, Hyper-V may treat a 1-page flush the same if the
    > > > address points to a huge page, it still would be better
    > > > to use the correct size of huge page. Also introduce
    > > > a helper function to do range-based flushing when a direct
    > > > SP is dropped, which would help prevent future buggy use
    > > > of kvm_flush_remote_tlbs_with_address() in such case.
    > > >
    > > > Fixes: c3134ce240eed ("KVM: Replace old tlb flush function with new one to flush a specified range.")
    > > > Suggested-by: David Matlack <dmatlack@google.com>
    > > > Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
    > > > ---
    > > > arch/x86/kvm/mmu/mmu.c | 10 +++++++++-
    > > > 1 file changed, 9 insertions(+), 1 deletion(-)
    > > >
    > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
    > > > index e418ef3ecfcb..a3578abd8bbc 100644
    > > > --- a/arch/x86/kvm/mmu/mmu.c
    > > > +++ b/arch/x86/kvm/mmu/mmu.c
    > > > @@ -260,6 +260,14 @@ void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
    > > > kvm_flush_remote_tlbs_with_range(kvm, &range);
    > > > }
    > > >
    > > > +/* Flush all memory mapped by the given direct SP. */
    > > > +static void kvm_flush_remote_tlbs_direct_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
    > > > +{
    > > > + WARN_ON_ONCE(!sp->role.direct);
    > > > + kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
    > > > + KVM_PAGES_PER_HPAGE(sp->role.level + 1));

    Do we need "+1" here? sp->role.level=1 means 4k page.
    I think here should be “KVM_PAGES_PER_HPAGE(sp->role.level)”

    > >
    > > nit: I think it would make sense to introduce
    > > kvm_flush_remote_tlbs_gfn() in this patch since you are going to
    > > eventually use it here anyway.
    > >
    > OK, I'll do it in the next version. Thanks!
    >
    > > > +}
    > > > +
    > > > static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
    > > > unsigned int access)
    > > > {
    > > > @@ -2341,7 +2349,7 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
    > > > return;
    > > >
    > > > drop_parent_pte(child, sptep);
    > > > - kvm_flush_remote_tlbs_with_address(vcpu->kvm, child->gfn, 1);
    > > > + kvm_flush_remote_tlbs_direct_sp(vcpu->kvm, child);
    > > > }
    > > > }
    > > >
    > > > --
    > > > 2.31.1
    > > >

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