Messages in this thread | | | Date | Thu, 31 Mar 2022 00:16:59 +0200 | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH 3/5] KVM: nSVM: Don't forget about L1-injected events |
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On 30.03.2022 23:59, Sean Christopherson wrote: > On Thu, Mar 10, 2022, Maciej S. Szmigiero wrote: >> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com> >> >> In SVM synthetic software interrupts or INT3 or INTO exception that L1 >> wants to inject into its L2 guest are forgotten if there is an intervening >> L0 VMEXIT during their delivery. >> >> They are re-injected correctly with VMX, however. >> >> This is because there is an assumption in SVM that such exceptions will be >> re-delivered by simply re-executing the current instruction. >> Which might not be true if this is a synthetic exception injected by L1, >> since in this case the re-executed instruction will be one already in L2, >> not the VMRUN instruction in L1 that attempted the injection. >> >> Leave the pending L1 -> L2 event in svm->nested.ctl.event_inj{,err} until >> it is either re-injected successfully or returned to L1 upon a nested >> VMEXIT. >> Make sure to always re-queue such event if returned in EXITINTINFO. >> >> The handling of L0 -> {L1, L2} event re-injection is left as-is to avoid >> unforeseen regressions. >> >> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com> >> --- > > ... > >> @@ -3627,6 +3632,14 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu) >> if (!(exitintinfo & SVM_EXITINTINFO_VALID)) >> return; >> >> + /* L1 -> L2 event re-injection needs a different handling */ >> + if (is_guest_mode(vcpu) && >> + exit_during_event_injection(svm, svm->nested.ctl.event_inj, >> + svm->nested.ctl.event_inj_err)) { >> + nested_svm_maybe_reinject(vcpu); > > Why is this manually re-injecting? More specifically, why does the below (out of > sight in the diff) code that re-queues the exception/interrupt not work? The > re-queued event should be picked up by nested_save_pending_event_to_vmcb12() and > propagatred to vmcb12.
A L1 -> L2 injected event should either be re-injected until successfully injected into L2 or propagated to VMCB12 if there is a nested VMEXIT during its delivery.
svm_complete_interrupts() does not do such re-injection in some cases (soft interrupts, soft exceptions, #VC) - it is trying to resort to emulation instead, which is incorrect in this case.
I think it's better to split out this L1 -> L2 nested case to a separate function in nested.c rather than to fill svm_complete_interrupts() in already very large svm.c with "if" blocks here and there.
Thanks, Maciej
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