The effective values of the guest CR0 and CR4 registers may differ from those included in the VMCS12. In particular, disabling EPT forces CR4.PAE=1 and disabling unrestricted guest mode forces CR0.PG=CR0.PE=1.
Therefore, checks on these bits cannot be delegated to the processor and must be performed by KVM.
Reported-by: Reima ISHII ishiir@g.ecc.u-tokyo.ac.jp Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com --- arch/x86/kvm/vmx/nested.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index d93c715cda6a..43693e4772ff 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3047,6 +3047,19 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu, vmcs12->guest_ia32_perf_global_ctrl))) return -EINVAL;
+ if (CC((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG)) + return -EINVAL; + +#ifdef CONFIG_X86_64 + ia32e = !!(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE); +#else + ia32e = false; +#endif + if (CC(ia32e && + (!(vmcs12->guest_cr4 & X86_CR4_PAE) || + !(vmcs12->guest_cr0 & X86_CR0_PG)))) + return -EINVAL; + /* * If the load IA32_EFER VM-entry control is 1, the following checks * are performed on the field for the IA32_EFER MSR: @@ -3058,7 +3071,6 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu, */ if (to_vmx(vcpu)->nested.nested_run_pending && (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER)) { - ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0; if (CC(!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer)) || CC(ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA)) || CC(((vmcs12->guest_cr0 & X86_CR0_PG) &&
On Fri, Mar 10, 2023, Paolo Bonzini wrote:
The effective values of the guest CR0 and CR4 registers may differ from those included in the VMCS12. In particular, disabling EPT forces CR4.PAE=1 and disabling unrestricted guest mode forces CR0.PG=CR0.PE=1.
Therefore, checks on these bits cannot be delegated to the processor and must be performed by KVM.
Reported-by: Reima ISHII ishiir@g.ecc.u-tokyo.ac.jp Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com
arch/x86/kvm/vmx/nested.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index d93c715cda6a..43693e4772ff 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -3047,6 +3047,19 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu, vmcs12->guest_ia32_perf_global_ctrl))) return -EINVAL;
- if (CC((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG))
return -EINVAL;+#ifdef CONFIG_X86_64
The #ifdef isn't necessary, attempting to set for a 32-bit host should be rejected by nested_vmx_check_controls() since nested_vmx_setup_ctls_msrs() clears the bit. Ditto for the host logic related to VM_EXIT_HOST_ADDR_SPACE_SIZE, which looks suspiciously similar ;-)
I'd rather delete the #ifdef in nested_vmx_check_host_state() and do something similar here, e.g.
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index 7c4f5ca405c7..3e367ec5086a 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2903,7 +2903,7 @@ static int nested_vmx_check_address_space_size(struct kvm_vcpu *vcpu, static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) { - bool ia32e; + bool ia32e = !!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE);
if (CC(!nested_host_cr0_valid(vcpu, vmcs12->host_cr0)) || CC(!nested_host_cr4_valid(vcpu, vmcs12->host_cr4)) || @@ -2923,12 +2923,6 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu, vmcs12->host_ia32_perf_global_ctrl))) return -EINVAL;
-#ifdef CONFIG_X86_64 - ia32e = !!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE); -#else - ia32e = false; -#endif - if (ia32e) { if (CC(!(vmcs12->host_cr4 & X86_CR4_PAE))) return -EINVAL;
- ia32e = !!(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE);
+#else
- ia32e = false;
+#endif
- if (CC(ia32e &&
(!(vmcs12->guest_cr4 & X86_CR4_PAE) ||!(vmcs12->guest_cr0 & X86_CR0_PG))))return -EINVAL;
This is a lot easier to read IMO, and has the advantage of more precisely identifying the failure in the tracepoint.
if (CC(ia32e && !(vmcs12->guest_cr4 & X86_CR4_PAE)) || CC(ia32e && !(vmcs12->guest_cr4 & X86_CR0_PG))) return -EINVAL;
- /*
- If the load IA32_EFER VM-entry control is 1, the following checks
- are performed on the field for the IA32_EFER MSR:
@@ -3058,7 +3071,6 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu, */ if (to_vmx(vcpu)->nested.nested_run_pending && (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER)) {
ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0;-- 2.39.1
On Sat, Mar 11, 2023 at 1:17 AM Sean Christopherson seanjc@google.com wrote:
@@ -3047,6 +3047,19 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu, vmcs12->guest_ia32_perf_global_ctrl))) return -EINVAL;
if (CC((vmcs12->guest_cr0 & (X86_CR0_PG | X86_CR0_PE)) == X86_CR0_PG))return -EINVAL;+#ifdef CONFIG_X86_64
The #ifdef isn't necessary, attempting to set for a 32-bit host should be rejected by nested_vmx_check_controls() since nested_vmx_setup_ctls_msrs() clears the bit. Ditto for the host logic related to VM_EXIT_HOST_ADDR_SPACE_SIZE, which looks suspiciously similar ;-)
Yeah, I noticed that too and decided that the idea could have been to allow some dead code elimination on 32-bit kernels, so I copied what the host state checks were doing. But if you prefer the more compact way I am absolutely not going to complain.
if (CC(ia32e &&(!(vmcs12->guest_cr4 & X86_CR4_PAE) ||!(vmcs12->guest_cr0 & X86_CR0_PG))))return -EINVAL;This is a lot easier to read IMO, and has the advantage of more precisely identifying the failure in the tracepoint.
if (CC(ia32e && !(vmcs12->guest_cr4 & X86_CR4_PAE)) || CC(ia32e && !(vmcs12->guest_cr4 & X86_CR0_PG))) return -EINVAL;
Looks good. I squashed everything in.
Paolo
linux-stable-mirror@lists.linaro.org
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Paolo Bonzini -
Sean Christopherson