This is a note to let you know that I've just added the patch titled KVM: nVMX: don't use vcpu->arch.efer when checking host state on nested state load to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-nvmx-don-t-use-vcpu-arch.efer-when-checking-host-state-on-nested-state-load.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From af957eebfcc17433ee83ab85b1195a933ab5049c Mon Sep 17 00:00:00 2001 From: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Date: Mon, 15 Nov 2021 15:18:36 +0200 Subject: KVM: nVMX: don't use vcpu->arch.efer when checking host state on nested state load From: Maxim Levitsky <mlevitsk@xxxxxxxxxx> commit af957eebfcc17433ee83ab85b1195a933ab5049c upstream. When loading nested state, don't use check vcpu->arch.efer to get the L1 host's 64-bit vs. 32-bit state and don't check it for consistency with respect to VM_EXIT_HOST_ADDR_SPACE_SIZE, as register state in vCPU may be stale when KVM_SET_NESTED_STATE is called---and architecturally does not exist. When restoring L2 state in KVM, the CPU is placed in non-root where nested VMX code has no snapshot of L1 host state: VMX (conditionally) loads host state fields loaded on VM-exit, but they need not correspond to the state before entry. A simple case occurs in KVM itself, where the host RIP field points to vmx_vmexit rather than the instruction following vmlaunch/vmresume. However, for the particular case of L1 being in 32- or 64-bit mode on entry, the exit controls can be treated instead as the source of truth regarding the state of L1 on entry, and can be used to check that vmcs12.VM_EXIT_HOST_ADDR_SPACE_SIZE matches vmcs12.HOST_EFER if vmcs12.VM_EXIT_LOAD_IA32_EFER is set. The consistency check on CPU EFER vs. vmcs12.VM_EXIT_HOST_ADDR_SPACE_SIZE, instead, happens only on VM-Enter. That's because, again, there's conceptually no "current" L1 EFER to check on KVM_SET_NESTED_STATE. Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Message-Id: <20211115131837.195527-2-mlevitsk@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/vmx/nested.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -2851,6 +2851,17 @@ static int nested_vmx_check_controls(str return 0; } +static int nested_vmx_check_address_space_size(struct kvm_vcpu *vcpu, + struct vmcs12 *vmcs12) +{ +#ifdef CONFIG_X86_64 + if (CC(!!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) != + !!(vcpu->arch.efer & EFER_LMA))) + return -EINVAL; +#endif + return 0; +} + static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) { @@ -2875,18 +2886,16 @@ static int nested_vmx_check_host_state(s return -EINVAL; #ifdef CONFIG_X86_64 - ia32e = !!(vcpu->arch.efer & EFER_LMA); + ia32e = !!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE); #else ia32e = false; #endif if (ia32e) { - if (CC(!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE)) || - CC(!(vmcs12->host_cr4 & X86_CR4_PAE))) + if (CC(!(vmcs12->host_cr4 & X86_CR4_PAE))) return -EINVAL; } else { - if (CC(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) || - CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) || + if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) || CC(vmcs12->host_cr4 & X86_CR4_PCIDE) || CC((vmcs12->host_rip) >> 32)) return -EINVAL; @@ -3555,6 +3564,9 @@ static int nested_vmx_run(struct kvm_vcp if (nested_vmx_check_controls(vcpu, vmcs12)) return nested_vmx_fail(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD); + if (nested_vmx_check_address_space_size(vcpu, vmcs12)) + return nested_vmx_fail(vcpu, VMXERR_ENTRY_INVALID_HOST_STATE_FIELD); + if (nested_vmx_check_host_state(vcpu, vmcs12)) return nested_vmx_fail(vcpu, VMXERR_ENTRY_INVALID_HOST_STATE_FIELD); Patches currently in stable-queue which might be from mlevitsk@xxxxxxxxxx are queue-5.10/kvm-nvmx-don-t-use-vcpu-arch.efer-when-checking-host-state-on-nested-state-load.patch