Re: [Xen-devel] [PATCH v2 4/8] xen: Use the correctly the Xen memory terminologies

[Boris Ostrovsky]

On 08/05/2015 08:33 AM, Julien Grall wrote:
> On 05/08/15 13:19, Boris Ostrovsky wrote:
> > On 08/05/2015 06:51 AM, Julien Grall wrote:
> > > > > diff --git a/drivers/video/fbdev/xen-fbfront.c
> > > > > b/drivers/video/fbdev/xen-fbfront.c
> > > > > index 09dc447..25e3cce 100644
> > > > > --- a/drivers/video/fbdev/xen-fbfront.c
> > > > > +++ b/drivers/video/fbdev/xen-fbfront.c
> > > > > @@ -539,7 +539,7 @@ static int xenfb_remove(struct xenbus_device *dev)
> > > > >       static unsigned long vmalloc_to_mfn(void *address)
> > > > >     {
> > > > > -    return pfn_to_mfn(vmalloc_to_pfn(address));
> > > > > +    return pfn_to_gfn(vmalloc_to_pfn(address));
> > > > >     }
> > > > Are you sure? This will return vmalloc_to_pfn(address)).
> > > I guess you mean vmalloc_to_mfn will return vmalloc_to_pfn?
> > >
> > > If so, it will be only the case on auto-translated case (because pfn ==
> > > gfn). In the case of PV, the mfn will be returned.
> > How will mfn be returned on PV when pfn_to_gfn() is an identity function?
> >
> > static inline unsigned long pfn_to_gfn(unsigned long pfn)
> >   {
> >       return pfn;
> >   }
> The identity function is only for ARM guest which are always
> auto-translated (arch/arm/include/asm/xen/page.h).
>
> The x86 version contains a check if the guest is auto-translated or not
> (arch/x86/include/asm/xen/page.):
>
> static inline unsigned long pfn_to_gfn(unsigned long pfn)
> {
>          if (xen_feature(XENFEAT_auto_translated_physmap))
>                  return pfn;
>          else
>                  return pfn_to_mfn(pfn);
> }

Of course --- I was looking at the top of the patch and didn't realize 
it was ARM changes. Sorry for the noise.

-boris
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