Re: [Xen-devel] [PATCH 1/2] x86/HVM: latch linear->phys translation results

[Tim Deegan <tim@xxxxxxx>]

At 12:54 +0100 on 09 Jun (1465476894), Andrew Cooper wrote:
> On 08/06/16 14:09, Jan Beulich wrote:
> > ... to avoid re-doing the same translation later again (in a retry, for
> > example). This doesn't help very often according to my testing, but
> > it's pretty cheap to have, and will be of further use subsequently.
> >
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >
> > --- a/xen/arch/x86/hvm/emulate.c
> > +++ b/xen/arch/x86/hvm/emulate.c
> > @@ -678,6 +678,19 @@ static struct hvm_mmio_cache *hvmemul_fi
> >      return cache;
> >  }
> >  
> > +static void latch_linear_to_phys(struct hvm_vcpu_io *vio, unsigned long 
> > gla,
> > +                                 unsigned long gpa, bool_t write)
> > +{
> > +    if ( vio->mmio_access.gla_valid )
> > +        return;
> > +
> > +    vio->mmio_gva = gla & PAGE_MASK;
> 
> This suggest that mmio_vga is mis-named.
> 
> Looking at the uses, handle_mmio_with_translation() is used
> inconsistently, with virtual addresses from the shadow code, but linear
> addresses from nested hap code.
> 
> Clearly one of these two users are buggy for guests running in a non
> flat way, and it looks to be the shadow side which is buggy.

Yes, the naming in the shadow code is incorrect.  Shadow code, along
with a lot of Xen code, uses "virtual" to refer to what the manuals
call linear addresses, i.e. the inputs to paging.  IIRC it was only
with the introduction of HAP hardware interfaces that we started using
the term "linear" widely in Xen code.

I will ack a mechanical renaming if you like, though beware of public
interfaces with the old name, and common code ("linear" being an x86
term).

Tim.

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