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    SubjectRe: [PATCH v2 1/3] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid
    On Fri, Feb 19, 2021 at 6:46 AM David Edmondson
    <david.edmondson@oracle.com> wrote:
    >
    > If the VM entry/exit controls for loading/saving MSR_EFER are either
    > not available (an older processor or explicitly disabled) or not
    > used (host and guest values are the same), reading GUEST_IA32_EFER
    > from the VMCS returns an inaccurate value.
    >
    > Because of this, in dump_vmcs() don't use GUEST_IA32_EFER to decide
    > whether to print the PDPTRs - do so if the EPT is in use and CR4.PAE
    > is set.
    >
    > Fixes: 4eb64dce8d0a ("KVM: x86: dump VMCS on invalid entry")
    > Signed-off-by: David Edmondson <david.edmondson@oracle.com>
    > ---
    > arch/x86/kvm/vmx/vmx.c | 8 +++-----
    > 1 file changed, 3 insertions(+), 5 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    > index eb69fef57485..818051c9fa10 100644
    > --- a/arch/x86/kvm/vmx/vmx.c
    > +++ b/arch/x86/kvm/vmx/vmx.c
    > @@ -5759,7 +5759,6 @@ void dump_vmcs(void)
    > u32 vmentry_ctl, vmexit_ctl;
    > u32 cpu_based_exec_ctrl, pin_based_exec_ctrl, secondary_exec_control;
    > unsigned long cr4;
    > - u64 efer;
    >
    > if (!dump_invalid_vmcs) {
    > pr_warn_ratelimited("set kvm_intel.dump_invalid_vmcs=1 to dump internal KVM state.\n");
    > @@ -5771,7 +5770,6 @@ void dump_vmcs(void)
    > cpu_based_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
    > pin_based_exec_ctrl = vmcs_read32(PIN_BASED_VM_EXEC_CONTROL);
    > cr4 = vmcs_readl(GUEST_CR4);
    > - efer = vmcs_read64(GUEST_IA32_EFER);
    > secondary_exec_control = 0;
    > if (cpu_has_secondary_exec_ctrls())
    > secondary_exec_control = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
    > @@ -5784,8 +5782,7 @@ void dump_vmcs(void)
    > cr4, vmcs_readl(CR4_READ_SHADOW), vmcs_readl(CR4_GUEST_HOST_MASK));
    > pr_err("CR3 = 0x%016lx\n", vmcs_readl(GUEST_CR3));
    > if ((secondary_exec_control & SECONDARY_EXEC_ENABLE_EPT) &&
    > - (cr4 & X86_CR4_PAE) && !(efer & EFER_LMA))
    > - {
    > + (cr4 & X86_CR4_PAE)) {

    Assuming that we really want to restrict the printing of the PDPTEs, I
    think you also need to test "cr0 & CR0.PG" (cf. section 26.3.1.6 of
    the SDM, volume 3).

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