diff options
author | Sean Christopherson <sean.j.christopherson@intel.com> | 2019-09-27 14:45:16 -0700 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-10-22 13:34:07 +0200 |
commit | 04f11ef45810da5ae2542dd78cc353f3761bd2cb (patch) | |
tree | 00877eeaf65a19f4dd5c917da8009b4d768a4627 /arch/x86 | |
parent | 83af5e65a89547633bab7278564219ca8e68b968 (diff) |
KVM: nVMX: Always write vmcs02.GUEST_CR3 during nested VM-Enter
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>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/kvm/vmx/nested.c | 10 | ||||
-rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 10 |
2 files changed, 17 insertions, 3 deletions
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index e76eb4f07f6c..d93ddc79a595 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2418,6 +2418,16 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, entry_failure_code)) return -EINVAL; + /* + * Immediately write vmcs02.GUEST_CR3. It will be propagated to vmcs12 + * on nested VM-Exit, which can occur without actually running L2 and + * thus without hitting vmx_set_cr3(), e.g. if L1 is entering L2 with + * vmcs12.GUEST_ACTIVITYSTATE=HLT, in which case KVM will intercept the + * transition to HLT instead of running L2. + */ + if (enable_ept) + vmcs_writel(GUEST_CR3, vmcs12->guest_cr3); + /* Late preparation of GUEST_PDPTRs now that EFER and CRs are set. */ if (load_guest_pdptrs_vmcs12 && nested_cpu_has_ept(vmcs12) && is_pae_paging(vcpu)) { diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 8f01019295a1..04603f53ca36 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -2989,6 +2989,7 @@ u64 construct_eptp(struct kvm_vcpu *vcpu, unsigned long root_hpa) void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) { struct kvm *kvm = vcpu->kvm; + bool update_guest_cr3 = true; unsigned long guest_cr3; u64 eptp; @@ -3005,15 +3006,18 @@ void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3) spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock); } - if (enable_unrestricted_guest || is_paging(vcpu) || - is_guest_mode(vcpu)) + /* Loading vmcs02.GUEST_CR3 is handled by nested VM-Enter. */ + if (is_guest_mode(vcpu)) + update_guest_cr3 = false; + else if (enable_unrestricted_guest || is_paging(vcpu)) guest_cr3 = kvm_read_cr3(vcpu); else guest_cr3 = to_kvm_vmx(kvm)->ept_identity_map_addr; ept_load_pdptrs(vcpu); } - vmcs_writel(GUEST_CR3, guest_cr3); + if (update_guest_cr3) + vmcs_writel(GUEST_CR3, guest_cr3); } int vmx_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) |