Re: [PATCH v4 09/46] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler

Excerpts from Paul Mackerras's message of March 31, 2021 2:54 pm:

On Tue, Mar 23, 2021 at 11:02:28AM +1000, Nicholas Piggin wrote:

quoted

The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with
MSR[IR]=0, so the faults of concern are the d-side ones caused by access
to guest context by the hypervisor.

Instruction breakpoint interrupts are not a concern here. It's unlikely
any good would come of causing breaks in this code, but skipping the
instruction that caused it won't help matters (e.g., skip the mtmsr that
sets MSR[DR]=0 or clears KVM_GUEST_MODE_SKIP).

Reviewed-by: Daniel Axtens <redacted>
Reviewed-by: Fabiano Rosas <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

It might be worth noting in the commit message that the 0x1300
interrupt was dropped from the architecture a long time ago and is not
generated by P7, P8, P9 or P10.

Good background, I'll add that.

Thanks,
Nick

Acked-by: Paul Mackerras <redacted>