Re: [Xen-devel] [PATCH] x86/HVM: fix interaction between internal and extern emulation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.11.17 at 12:58, <Paul.Durrant@xxxxxxxxxx> wrote:
>>  -----Original Message-----
>> From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf
>> Of Paul Durrant
>> Sent: 28 November 2017 11:31
>> To: 'Jan Beulich' <JBeulich@xxxxxxxx>
>> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Julien Grall
>> <julien.grall@xxxxxxx>; xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
>> Subject: Re: [Xen-devel] [PATCH] x86/HVM: fix interaction between internal
>> and extern emulation
>> 
>> > -----Original Message-----
>> > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> > Sent: 28 November 2017 11:26
>> > To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
>> > Cc: Julien Grall <julien.grall@xxxxxxx>; Andrew Cooper
>> > <Andrew.Cooper3@xxxxxxxxxx>; xen-devel <xen-
>> > devel@xxxxxxxxxxxxxxxxxxxx>
>> > Subject: RE: [PATCH] x86/HVM: fix interaction between internal and extern
>> > emulation
>> >
>> > >>> On 28.11.17 at 12:06, <Paul.Durrant@xxxxxxxxxx> wrote:
>> > > Yes, it appears that mmio_retry is only set when the underlying
>> emulation
>> > > returned X86EMUL_OKAY but not all reps were completed. If the
>> > underlying
>> > > emulation did not return X86EMUL_RETRY then I can't figure out why
>> > > vio->io_completion should need to be set to anything other than
>> > > HVMIO_no_completion since any other return value indicates there
>> should
>> > be
>> > > nothing pending.
>> >
>> > So am I getting it right that you're suggesting to remove the
>> > mmio_retry part of the condition in hvm_emulate_one_insn()?
>> > That looks like it might work (I was previously only considering
>> > to get rid of mmio_retry altogether, and that didn't look like a
>> > viable route).
>> 
>> Yes, that's what I'm suggesting. I really can't see why it is needed. It 
> could
>> have been a mistake in my original patches or a semantic change in a
>> subsequent patch, but it certainly looks wrong in current context.
>> Andrew has just sent me his xtf repro so I'll give the change a go with 
> that.
> 
> Yes, this patch fixed the problem for me. I'll do some more tests to check 
> for collateral damage now... If it's all good, do you want me to submit it or 
> do you want to send it as a v2 of your patch?

It's yours, so please submit it (perhaps nevertheless as v2). Feel
free to add my R-b right away if no other change turns out
necessary.

Jan


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