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    Subject[PATCH v2 09/10] KVM: x86: drop KVM_PV_REASON_PAGE_READY case from kvm_handle_page_fault()
    Date
    KVM guest code in Linux enables APF only when KVM_FEATURE_ASYNC_PF_INT
    is supported, this means we will never see KVM_PV_REASON_PAGE_READY
    when handling page fault vmexit in KVM.

    While on it, make sure we only follow genuine page fault path when
    APF reason is zero. If we happen to see something else this means
    that the underlying hypervisor is misbehaving. Leave WARN_ON_ONCE()
    to catch that.

    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    ---
    arch/x86/kvm/mmu/mmu.c | 17 ++++++-----------
    1 file changed, 6 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
    index 7fa5253237b2..1bb7a8c6c28e 100644
    --- a/arch/x86/kvm/mmu/mmu.c
    +++ b/arch/x86/kvm/mmu/mmu.c
    @@ -4178,6 +4178,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
    u64 fault_address, char *insn, int insn_len)
    {
    int r = 1;
    + u32 flags = vcpu->arch.apf.host_apf_flags;

    #ifndef CONFIG_X86_64
    /* A 64-bit CR2 should be impossible on 32-bit KVM. */
    @@ -4186,28 +4187,22 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
    #endif

    vcpu->arch.l1tf_flush_l1d = true;
    - switch (vcpu->arch.apf.host_apf_flags) {
    - default:
    + if (!flags) {
    trace_kvm_page_fault(fault_address, error_code);

    if (kvm_event_needs_reinjection(vcpu))
    kvm_mmu_unprotect_page_virt(vcpu, fault_address);
    r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
    insn_len);
    - break;
    - case KVM_PV_REASON_PAGE_NOT_PRESENT:
    + } else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) {
    vcpu->arch.apf.host_apf_flags = 0;
    local_irq_disable();
    kvm_async_pf_task_wait(fault_address, 0);
    local_irq_enable();
    - break;
    - case KVM_PV_REASON_PAGE_READY:
    - vcpu->arch.apf.host_apf_flags = 0;
    - local_irq_disable();
    - kvm_async_pf_task_wake(fault_address);
    - local_irq_enable();
    - break;
    + } else {
    + WARN_ONCE(1, "Unexpected host async PF flags: %x\n", flags);
    }
    +
    return r;
    }
    EXPORT_SYMBOL_GPL(kvm_handle_page_fault);
    --
    2.25.4
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