diff options
Diffstat (limited to 'arch/x86/kvm/svm/nested.c')
| -rw-r--r-- | arch/x86/kvm/svm/nested.c | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 834b67672d50..8427a48b8b7a 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -678,6 +678,33 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm, vmcb02->control.iopm_base_pa = vmcb01->control.iopm_base_pa; vmcb02->control.msrpm_base_pa = vmcb01->control.msrpm_base_pa; + /* + * Stash vmcb02's counter if the guest hasn't moved past the guilty + * instruction; otherwise, reset the counter to '0'. + * + * In order to detect if L2 has made forward progress or not, track the + * RIP at which a bus lock has occurred on a per-vmcb12 basis. If RIP + * is changed, guest has clearly made forward progress, bus_lock_counter + * still remained '1', so reset bus_lock_counter to '0'. Eg. In the + * scenario, where a buslock happened in L1 before VMRUN, the bus lock + * firmly happened on an instruction in the past. Even if vmcb01's + * counter is still '1', (because the guilty instruction got patched), + * the vCPU has clearly made forward progress and so KVM should reset + * vmcb02's counter to '0'. + * + * If the RIP hasn't changed, stash the bus lock counter at nested VMRUN + * to prevent the same guilty instruction from triggering a VM-Exit. Eg. + * if userspace rate-limits the vCPU, then it's entirely possible that + * L1's tick interrupt is pending by the time userspace re-runs the + * vCPU. If KVM unconditionally clears the counter on VMRUN, then when + * L1 re-enters L2, the same instruction will trigger a VM-Exit and the + * entire cycle start over. + */ + if (vmcb02->save.rip && (svm->nested.ctl.bus_lock_rip == vmcb02->save.rip)) + vmcb02->control.bus_lock_counter = 1; + else + vmcb02->control.bus_lock_counter = 0; + /* Done at vmrun: asid. */ /* Also overwritten later if necessary. */ @@ -1039,8 +1066,17 @@ int nested_svm_vmexit(struct vcpu_svm *svm) } + /* + * Invalidate bus_lock_rip unless KVM is still waiting for the guest + * to make forward progress before re-enabling bus lock detection. + */ + if (!vmcb02->control.bus_lock_counter) + svm->nested.ctl.bus_lock_rip = INVALID_GPA; + nested_svm_copy_common_state(svm->nested.vmcb02.ptr, svm->vmcb01.ptr); + kvm_nested_vmexit_handle_ibrs(vcpu); + svm_switch_vmcb(svm, &svm->vmcb01); /* |