+Isaku and Xiaoyao On Mon, Nov 30, 2020, Paolo Bonzini wrote: > On 30/11/20 19:14, Sean Christopherson wrote: > > > > TDX also selectively blocks/skips portions of other ioctl()s so that the > > > > TDX code itself can yell loudly if e.g. .get_cpl() is invoked. The event > > > > injection restrictions are due to direct injection not being allowed (except > > > > for NMIs); all IRQs have to be routed through APICv (posted interrupts) and > > > > exception injection is completely disallowed. > > > > > > > > kvm_vcpu_ioctl_x86_get_vcpu_events: > > > > if (!vcpu->kvm->arch.guest_state_protected) > > > > events->interrupt.shadow = kvm_x86_ops.get_interrupt_shadow(vcpu); > > > Perhaps an alternative implementation can enter the vCPU with immediate exit > > > until no events are pending, and then return all zeroes? > > > > This can't work. If the guest has STI blocking, e.g. it did STI->TDVMCALL with > > a valid vIRQ in GUEST_RVI, then events->interrupt.shadow should technically be > > non-zero to reflect the STI blocking. But, the immediate exit (a hardware IRQ > > for TDX guests) will cause VM-Exit before the guest can execute any instructions > > and thus the guest will never clear STI blocking and never consume the pending > > event. Or there could be a valid vIRQ, but GUEST_RFLAGS.IF=0, in which case KVM > > would need to run the guest for an indeterminate amount of time to wait for the > > vIRQ to be consumed. > > Delayed interrupts are fine, since they are injected according to RVI and > the posted interrupt descriptor. I'm thinking more of events (exceptions > and interrupts) that caused an EPT violation exit and were recorded in the > IDT-vectored info field. Ah. As is, I don't believe KVM has access to this information. TDX-Module handles the actual EPT violation, as well as event reinjection. The EPT violation reported by SEAMRET is synthesized, and IIRC the IDT-vectoring field is not readable. Regardless, is there an actual a problem with having a "pending" exception that isn't reported to userspace? Obviously the info needs to be migrated, but that will be taken care of by virtue of migrating the VMCS.
