Re: [PATCH] KVM: s390: vsie: retry SIE instruction on host intercepts

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Am 04.03.24 um 09:35 schrieb David Hildenbrand:
On 01.03.24 21:43, Eric Farman wrote:
It's possible that SIE exits for work that the host needs to perform
rather than something that is intended for the guest.

A Linux guest will ignore this intercept code since there is nothing
for it to do, but a more robust solution would rewind the PSW back to
the SIE instruction. This will transparently resume the guest once
the host completes its work, without the guest needing to process
what is effectively a NOP and re-issue SIE itself.

I recall that 0-intercepts are valid by the architecture. Further, I recall that there were some rather tricky corner cases where avoiding 0-intercepts would not be that easy.

Now, it's been a while ago, and maybe I misremember. SoI'm trusting people with access to documentation can review this.

Yes, 0-intercepts are allowed, and this also happens when LPAR has an exit.
So this patch is not necessary, the question is if this would be an valuable optimization?

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