Messages in this thread Patch in this message | | | Subject | Re: [PATCH] KVM: nVMX: Fix nested bus lock VM exit | From | Xiaoyao Li <> | Date | Thu, 2 Sep 2021 09:32:07 +0800 |
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On 9/2/2021 2:08 AM, Sean Christopherson wrote: > On Fri, Aug 27, 2021, Chenyi Qiang wrote: >> Nested bus lock VM exits are not supported yet. If L2 triggers bus lock >> VM exit, it will be directed to L1 VMM, which would cause unexpected >> behavior. Therefore, handle L2's bus lock VM exits in L0 directly. >> >> Fixes: fe6b6bc802b4 ("KVM: VMX: Enable bus lock VM exit") >> Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com> >> --- >> arch/x86/kvm/vmx/nested.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >> index bc6327950657..754f53cf0f7a 100644 >> --- a/arch/x86/kvm/vmx/nested.c >> +++ b/arch/x86/kvm/vmx/nested.c >> @@ -5873,6 +5873,8 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu, >> case EXIT_REASON_VMFUNC: >> /* VM functions are emulated through L2->L0 vmexits. */ >> return true; >> + case EXIT_REASON_BUS_LOCK: >> + return true; > > Hmm, unless there is zero chance of ever exposing BUS_LOCK_DETECTION to L1, it > might be better to handle this in nested_vmx_l1_wants_exit(), e.g. > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > index b3f77d18eb5a..793534b7eaba 100644 > --- a/arch/x86/kvm/vmx/nested.c > +++ b/arch/x86/kvm/vmx/nested.c > @@ -6024,6 +6024,8 @@ static bool nested_vmx_l1_wants_exit(struct kvm_vcpu *vcpu, > SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE); > case EXIT_REASON_ENCLS: > return nested_vmx_exit_handled_encls(vcpu, vmcs12); > + case EXIT_REASON_BUS_LOCK: > + return nested_cpu_has2(vmcs12, SECONDARY_EXEC_BUS_LOCK_DETECTION);
yes, for now, it equals
return false;
because KVM doesn't expose it to L1.
> default: > return true; > } > > It's a rather roundabout way of reaching the same result, but I'd prefer to limit > nested_vmx_l0_wants_exit() to cases where L0 wants to handle the exit regardless > of what L1 wants. This kinda fits that model, but it's not really that L0 "wants" > the exit, it's that L1 can't want the exit. Does that make sense?
something like below has to be in nested_vmx_l0_wants_exit()
--- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -5873,6 +5873,8 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu, case EXIT_REASON_VMFUNC: /* VM functions are emulated through L2->L0 vmexits. */ return true; + case EXIT_REASON_BUS_LOCK: + return vcpu->kvm->arch.bus_lock_detection_enabled; default: break; }
L0 wants this VM exit because it enables BUS LOCK VM exit, not because L1 doesn't enable it.
> >> default: >> break; >> } >> -- >> 2.17.1 >>
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