• Sean Christopherson's avatar
    KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter · 04f11ef4
    Sean Christopherson authored
    Write the desired L2 CR3 into vmcs02.GUEST_CR3 during nested VM-Enter
    instead of deferring the VMWRITE until vmx_set_cr3().  If the VMWRITE
    is deferred, then KVM can consume a stale vmcs02.GUEST_CR3 when it
    refreshes vmcs12->guest_cr3 during nested_vmx_vmexit() if the emulated
    VM-Exit occurs without actually entering L2, e.g. if the nested run
    is squashed because nested VM-Enter (from L1) is putting L2 into HLT.
    
    Note, the above scenario can occur regardless of whether L1 is
    intercepting HLT, e.g. L1 can intercept HLT and then re-enter L2 with
    vmcs.GUEST_ACTIVITY_STATE=HALTED.  But practically speaking, a VMM will
    likely put a guest into HALTED if and only if it's not intercepting HLT.
    
    In an ideal world where EPT *requires* unrestricted guest (and vice
    versa), VMX could handle CR3 similar to how it handles RSP and RIP,
    e.g. mark CR3 dirty and conditionally load it at vmx_vcpu_run().  But
    the unrestricted guest silliness complicates the dirty tracking logic
    to the point that explicitly handling vmcs02.GUEST_CR3 during nested
    VM-Enter is a simpler overall implementation.
    
    Cc: stable@vger.kernel.org
    Reported-and-tested-by: default avatarReto Buerki <reet@codelabs.ch>
    Tested-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
    Reviewed-by: default avatarLiran Alon <liran.alon@oracle.com>
    Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
    Reviewed-by: default avatarJim Mattson <jmattson@google.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    04f11ef4
nested.c 186 KB