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


  • To: 'Jan Beulich' <JBeulich@xxxxxxxx>
  • From: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
  • Date: Tue, 28 Nov 2017 11:30:50 +0000
  • Accept-language: en-GB, en-US
  • Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Tue, 28 Nov 2017 11:30:57 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHTZ1nBSL0frxJLBUiA0SzbYP91yaMpi+hw///0fgCAABEpkP//8vqAgAAQ9HD///WUgAACivhgAABcaoD///WUAP//7vZg
  • Thread-topic: [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.

  Paul

  Paul

> 
> Jan


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