Messages in this thread | | | Subject | Re: [PATCH v8 2/5] x86/tdx: Add TDX Guest event notify interrupt support | From | Kai Huang <> | Date | Thu, 23 Jun 2022 21:46:41 +1200 |
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> > > > > That being said, if a TD has multiple devices, it cannot know whether the VMM > > will inject the removal event via the vector set by SetupEventNotifyInterrupt. > > And for the same device in the same TD, different VMMs may use different way to > > notify its removal. > > As per current design, If it is used for device removal, I think all registered > device drivers will get the notification and the individual device driver has > to check whether it is applicable for them.
The problem is there's no _specification_ around this. As I said above, I don't see why TDX architecture cannot support Qemu enumerated ACPI-based hotplug, which uses SCI. Maybe I am missing something here, but IMHO we should have some _specification_ around SetupEventNotifyInterrupt in GHCI.
> > If the SetupEventNotifyInterrupt TDVMCALL specification is extended to specify > the exact device or use case detail, then it can optimize the implementation. > > > > > It seems GetQuote is the only user of SetupEventNotifyInterrupt. Maybe we > > should just declare it is for GetQuote. > > Ok.
If you believe this is reasonable, perhaps you can drive the spec change.
> > > > > Isaku, what do you think? Does this make sense? > > > > > > > > In TDX guest, SetupEventNotifyInterrupt hypercall can be used by the > > > guest to specify which interrupt vector to use as an event-notify > > > vector to the VMM. Details about the SetupEventNotifyInterrupt > > > hypercall can be found in TDX Guest-Host Communication Interface > > > (GHCI) Specification, sec 3.5 "VP.VMCALL<SetupEventNotifyInterrupt>". > > > Add a tdx_hcall_set_notify_intr() helper function to implement the > > > SetupEventNotifyInterrupt hypercall. > > > > As you also used "can" above, the GHCI only says the VMM _CAN_ inject the vector > > set by SetupEventNotifyInterrupt, but not must (3.3 TDG.VP.VMCALL<GetQuote>). > > This means theoretically TD should implement pooling mode in case VMM doesn't > > support injecting event via vector done by SetupEventNotifyInterrupt? > > Yes. But GetQuote specification does not talk about the pooling mode > use case as well. So I think it is just a wording confusion.
It doesn't need to mention I think. "can" means VMM can choose to inject or not, but not must, which basically implies GetQuote should support pooling.
> > > > > Perhaps we should update the GHCI spec to use must.. > > Ok.
If you don't want to support pooling, I guess you'd better to improve the GHCI.
[...]
> > > > resource especially on server systems with a lot of CPUs. > > FWIW, this reservation is protected with CONFIG_INTEL_TDX_GUEST. So it will be > reserved only for TDX use case.
This reason doesn't stand. I think distributions basically tends to enable all Kconfig options so one binary works on all machines, so it can be (maybe likely) turned on even on bare-metal machines.
-- Thanks, -Kai
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