Re: [Xen-devel] [PATCH v1] x86/hvm: Generic instruction re-execution mechanism for execute faults

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Nov 21, 2018 at 10:28:18AM +0000, Alexandru Stefan ISAILA wrote:
> 
> 
> On 21.11.2018 11:56, Roger Pau Monné wrote:
> > On Mon, Nov 19, 2018 at 03:56:14PM +0000, Alexandru Stefan ISAILA wrote:
> >> On 19.11.2018 17:08, Roger Pau Monné wrote:
> > Also, after looking at the code I'm not sure I see why this needs to
> > be VMX specific, AFAICT it doesn't directly call any VMX functions?
> > 
> 
> It is vmx specific because svm does not have single step. We talked 
> about in the past about this and it turned out that it was to much 
> trouble to make a custom single step.

I still think this shouldn't be VMX specific, and you should just
return -EOPNOTSUPP if single stepping is not supported, just like
hvm_debug_op does. In fact I'm missing a helper to set single
stepping, which would be the right place to return -EOPNOTSUPP.

Then your rexec wouldn't need to know anything about the hardware and
would just attempt to set single stepping, failing if it cannot be
enabled.

Thanks, Roger.

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