KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter
commit 04f11ef458
upstream.
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: Reto Buerki <reet@codelabs.ch>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
parent
ff6900f46d
commit
815403a6ea
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@ -2418,6 +2418,16 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
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entry_failure_code))
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return -EINVAL;
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/*
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* Immediately write vmcs02.GUEST_CR3. It will be propagated to vmcs12
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* on nested VM-Exit, which can occur without actually running L2 and
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* thus without hitting vmx_set_cr3(), e.g. if L1 is entering L2 with
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* vmcs12.GUEST_ACTIVITYSTATE=HLT, in which case KVM will intercept the
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* transition to HLT instead of running L2.
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*/
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if (enable_ept)
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vmcs_writel(GUEST_CR3, vmcs12->guest_cr3);
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/* Late preparation of GUEST_PDPTRs now that EFER and CRs are set. */
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if (load_guest_pdptrs_vmcs12 && nested_cpu_has_ept(vmcs12) &&
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is_pae_paging(vcpu)) {
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@ -2995,6 +2995,7 @@ u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa)
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void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
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{
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struct kvm *kvm = vcpu->kvm;
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bool update_guest_cr3 = true;
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unsigned long guest_cr3;
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u64 eptp;
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@ -3011,15 +3012,18 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
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spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
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}
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if (enable_unrestricted_guest || is_paging(vcpu) ||
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is_guest_mode(vcpu))
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/* Loading vmcs02.GUEST_CR3 is handled by nested VM-Enter. */
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if (is_guest_mode(vcpu))
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update_guest_cr3 = false;
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else if (enable_unrestricted_guest || is_paging(vcpu))
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guest_cr3 = kvm_read_cr3(vcpu);
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else
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guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr;
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ept_load_pdptrs(vcpu);
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}
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vmcs_writel(GUEST_CR3, guest_cr3);
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if (update_guest_cr3)
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vmcs_writel(GUEST_CR3, guest_cr3);
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}
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int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
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