RE: [PATCH v3 01/13] viridian: don't blindly write to 32-bit registers is 'mode' is invalid

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 25 November 2020 07:52
> To: Paul Durrant <paul@xxxxxxx>
> Cc: Durrant, Paul <pdurrant@xxxxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>; 
> xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: RE: [EXTERNAL] [PATCH v3 01/13] viridian: don't blindly write to 
> 32-bit registers is 'mode'
> is invalid
> 
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> 
> On 24.11.2020 20:07, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@xxxxxxxxxx>
> >
> > If hvm_guest_x86_mode() returns something other than 8 or 4 then
> > viridian_hypercall() will return immediately but, on the way out, will write
> > back status as if 'mode' was 4. This patch simply makes it leave the 
> > registers
> > alone.
> >
> > NOTE: The formatting of the 'out' label and the switch statement are also
> >       adjusted as per CODING_STYLE.
> 
> Partly only as far as the latter goes:
> 
> > --- a/xen/arch/x86/hvm/viridian/viridian.c
> > +++ b/xen/arch/x86/hvm/viridian/viridian.c
> > @@ -692,13 +692,14 @@ int viridian_hypercall(struct cpu_user_regs *regs)
> >          break;
> >      }
> >
> > -out:
> > + out:
> >      output.result = status;
> >      switch (mode) {
> 
> This would want to be
> 
>     switch ( mode )
>     {
> 

Oh, yes.

> I guess this could easily be taken care of while committing.

Thanks,

  Paul

> 
> Jan