On Mon, Mar 24, 2025, Manali Shukla wrote:
- if (vmcb02->save.rip && (svm->nested.ctl.bus_lock_rip == vmcb02->save.rip)) {
vmcb02->control.bus_lock_counter = 1;svm->bus_lock_rip = svm->nested.ctl.bus_lock_rip;- } else {
vmcb02->control.bus_lock_counter = 0;- }
- svm->nested.ctl.bus_lock_rip = INVALID_GPA;
- /* Done at vmrun: asid. */
/* Also overwritten later if necessary. */ @@ -1039,6 +1069,18 @@ int nested_svm_vmexit(struct vcpu_svm *svm) }
- /*
* If bus_lock_counter is nonzero and the guest has not moved past the* guilty instruction, save bus_lock_rip in svm_nested_state. This will* help determine at nested VMRUN whether to stash vmcb02's counter or* reset it to '0'.*/- if (vmcb02->control.bus_lock_counter &&
svm->bus_lock_rip == vmcb02->save.rip)svm->nested.ctl.bus_lock_rip = svm->bus_lock_rip;- else
svm->nested.ctl.bus_lock_rip = INVALID_GPA;- nested_svm_copy_common_state(svm->nested.vmcb02.ptr, svm->vmcb01.ptr);
svm_switch_vmcb(svm, &svm->vmcb01);
...
+static int bus_lock_exit(struct kvm_vcpu *vcpu) +{
- struct vcpu_svm *svm = to_svm(vcpu);
- vcpu->run->exit_reason = KVM_EXIT_X86_BUS_LOCK;
- vcpu->run->flags |= KVM_RUN_X86_BUS_LOCK;
- vcpu->arch.cui_linear_rip = kvm_get_linear_rip(vcpu);
- svm->bus_lock_rip = vcpu->arch.cui_linear_rip;
- vcpu->arch.complete_userspace_io = complete_userspace_buslock;
- return 0;
+}
@@ -327,6 +328,7 @@ struct vcpu_svm { /* Guest GIF value, used when vGIF is not enabled */ bool guest_gif;
- u64 bus_lock_rip;
I don't think this field is necessary. Rather than unconditionally invalidate on nested VMRUN and then conditionally restore on nested #VMEXIT, just leave svm->nested.ctl.bus_lock_rip set on VMRUN and conditionally invalidate on #VMEXIT. And then in bus_lock_exit(), update the field if the exit occurred while L2 is active.
Completely untested:
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index a42ef7dd9143..98e065a93516 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -700,13 +700,10 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm, * 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)) { + if (vmcb02->save.rip && (svm->nested.ctl.bus_lock_rip == vmcb02->save.rip)) vmcb02->control.bus_lock_counter = 1; - svm->bus_lock_rip = svm->nested.ctl.bus_lock_rip; - } else { + else vmcb02->control.bus_lock_counter = 0; - } - svm->nested.ctl.bus_lock_rip = INVALID_GPA;
/* Done at vmrun: asid. */
@@ -1070,15 +1067,10 @@ int nested_svm_vmexit(struct vcpu_svm *svm) }
/* - * If bus_lock_counter is nonzero and the guest has not moved past the - * guilty instruction, save bus_lock_rip in svm_nested_state. This will - * help determine at nested VMRUN whether to stash vmcb02's counter or - * reset it to '0'. + * 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->bus_lock_rip == vmcb02->save.rip) - svm->nested.ctl.bus_lock_rip = svm->bus_lock_rip; - else + 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); diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index ea12e93ae983..11ce031323fd 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3333,9 +3333,10 @@ static int bus_lock_exit(struct kvm_vcpu *vcpu) vcpu->run->flags |= KVM_RUN_X86_BUS_LOCK;
vcpu->arch.cui_linear_rip = kvm_get_linear_rip(vcpu); - svm->bus_lock_rip = vcpu->arch.cui_linear_rip; vcpu->arch.complete_userspace_io = complete_userspace_buslock;
+ if (is_guest_mode(vcpu)) + svm->nested.ctl.bus_lock_rip = vcpu->arch.cui_linear_rip; return 0; }
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 7a4c5848c952..8667faccaedc 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -328,7 +328,6 @@ struct vcpu_svm {
/* Guest GIF value, used when vGIF is not enabled */ bool guest_gif; - u64 bus_lock_rip; };
struct svm_cpu_data {