[svsm-devel] Questions about Alternate Injection and timers

[Melody (Huibo) Wang]

Hi Jon,

I have a few questions I would like to clarify with you.

1. How do you envision the whole flow of injecting a timer interrupt into an
   AI-enabled guest with a SVSM?

   Qemu+KVM enables both the PIC and APIC by default and it tries to inject IRQ 0 as a timer
   interrupt but the spec talks only about vectors 31-255 will be handled
   by the SVSM What about 0-31 and 0 especially which is the PIC timer
   interrupt line?

2. In Coconut SVSM, we do not use "Injection Notification Vector" 0x50 to
   differentiate this #HV is for SVSM or lower VMPL, instead the SVSM is
   reading the extended interrupt information from the doorbell page
   automatically. At least I don't see where in the code we use vector 0x50 to
   do the differentiation.

   I would imagine we should use this vector to see if we need to read the
   doorbell page and after that we should clear this bit. We would need to
   make sure that KVM and SVSM are "compatible" in the pending event field,
   no?


As always, thanks for the help!

Melody