Messages in this thread | | | From | Peter Maydell <> | Date | Sun, 30 Nov 2014 10:20:19 +0000 | Subject | Re: [PATCH 5/7] KVM: arm64: guest debug, add support for single-step |
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On 30 November 2014 at 10:10, Christoffer Dall <christoffer.dall@linaro.org> wrote: > In any case, I think it was related to how userspace observes the state > of the CPU, because when you do the MMIO operation emulation in > userspace, currently if you observe the PC though GET_ONE_REG, you'll > see a PC pointing to the next instruction, not the one you're emulating > which is strange.
Also if we ever add support for userspace to say "this MMIO should fault" then we definitely need the PC-advance to happen afterwards, not before.
> Not sure what the relation to a guest single-stepping itself was.
I think it just came up in the course of that discussion, because single-step handling also needs to perform an action (clear PSTATE.SS) as part of the "advance over this insn" operation. But I think that you're right that doing the advance before dropping out to userspace is no worse for singlestep than it is for any other case.
-- PMM
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