From: Maxim Levitsky mlevitsk@redhat.com
commit b8453cdcf26020030da182f0156d7bf59ae5719f upstream.
Incorporate EFER.LMA into kvm_mmu_extended_role, as it used to compute the guest root level and is not reflected in kvm_mmu_page_role.level when TDP is in use. When simply running the guest, it is impossible for EFER.LMA and kvm_mmu.root_level to get out of sync, as the guest cannot transition from PAE paging to 64-bit paging without toggling CR0.PG, i.e. without first bouncing through a different MMU context. And stuffing guest state via KVM_SET_SREGS{,2} also ensures a full MMU context reset.
However, if KVM_SET_SREGS{,2} is followed by KVM_SET_NESTED_STATE, e.g. to set guest state when migrating the VM while L2 is active, the vCPU state will reflect L2, not L1. If L1 is using TDP for L2, then root_mmu will have been configured using L2's state, despite not being used for L2. If L2.EFER.LMA != L1.EFER.LMA, and L2 is using PAE paging, then root_mmu will be configured for guest PAE paging, but will match the mmu_role for 64-bit paging and cause KVM to not reconfigure root_mmu on the next nested VM-Exit.
Alternatively, the root_mmu's role could be invalidated after a successful KVM_SET_NESTED_STATE that yields vcpu->arch.mmu != vcpu->arch.root_mmu, i.e. that switches the active mmu to guest_mmu, but doing so is unnecessarily tricky, and not even needed if L1 and L2 do have the same role (e.g., they are both 64-bit guests and run with the same CR4).
Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Maxim Levitsky mlevitsk@redhat.com Message-Id: 20211115131837.195527-3-mlevitsk@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/mmu/mmu.c | 1 + 2 files changed, 2 insertions(+)
--- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -364,6 +364,7 @@ union kvm_mmu_extended_role { unsigned int cr4_smap:1; unsigned int cr4_smep:1; unsigned int cr4_la57:1; + unsigned int efer_lma:1; }; };
--- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4679,6 +4679,7 @@ static union kvm_mmu_extended_role kvm_c /* PKEY and LA57 are active iff long mode is active. */ ext.cr4_pke = ____is_efer_lma(regs) && ____is_cr4_pke(regs); ext.cr4_la57 = ____is_efer_lma(regs) && ____is_cr4_la57(regs); + ext.efer_lma = ____is_efer_lma(regs); }
ext.valid = 1;