Re: [Xen-devel] possible I/O emulation state machine issue

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.03.18 at 10:42, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 29 March 2018 07:27
>> 
>> Suppressing the stdvga port intercepts has, btw, not helped the
>> situation.
>> 
> 
> That surprises me. The whole string emulation should go out to QEMU without 
> being broken up in that case, and since it's an outsw I don't see why there 
> would be any retry of the linear->physical translation during completion.

See the patch sent earlier: HVMIO_mmio_completion means a full
second (or further) run through the emulator (which that patch
now avoids). Same would occur for an insn reading and writing
multiple memory locations, if at least the second one is in MMIO.
In that case we can't avoid the completion though, as the access
may additionally have been split (and we still need to execute
its later part(s)). To fully address this, I don't see a way around
recording completed steps (which is going to be a pretty intrusive
change as it looks).

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel