[RFC/PATCH 1/3] powerpc/kvm: Handle H_FAC_UNAVAIL when guest executes stop.

[Nicholas Piggin]

Gautham R. Shenoy's on March 31, 2020 10:10 pm:
> From: "Gautham R. Shenoy" <ego at linux.vnet.ibm.com>
> 
> If a guest executes a stop instruction when the hypervisor has set the
> PSSCR[ESL|EC] bits, the processor will throw an Hypervisor Facility
> Unavailable exception. Currently when we receive this exception, we
> only check if the exeception is generated due to a doorbell
> instruction, in which case we emulate it. For all other cases,
> including the case when the guest executes a stop-instruction, the
> hypervisor sends a PROGILL to the guest program, which results in a
> guest crash.
> 
> This patch adds code to handle the case when the hypervisor receives a
> H_FAC_UNAVAIL exception due to guest executing the stop
> instruction. The hypervisor increments the pc to the next instruction
> and resumes the guest as expected by the semantics of the
> PSSCR[ESL|EC] = 0 stop instruction.

This seems reasonable, I don't think we need to crash the guest here.

Thanks,
Nick