Re: [Xen-devel] [PATCH v2 0/2] Remove PAGE_SIZE from public headers

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 21 Oct 2016, Wei Liu wrote:
> On Thu, Oct 20, 2016 at 09:05:26PM +0100, Andrew Cooper wrote:
> > On 20/10/16 21:04, Stefano Stabellini wrote:
> > > On Thu, 20 Oct 2016, Andrew Cooper wrote:
> > >> On 20/10/16 20:09, Stefano Stabellini wrote:
> > >>> On Thu, 20 Oct 2016, Juergen Gross wrote:
> > >>>> On 19/10/16 21:21, stefano@xxxxxxxxxxx wrote:
> > >>>>> Reference to PAGE_SIZE slipped in to two public header files. QEMU 
> > >>>>> build on
> > >>>>> ARM64 is broken by this. PAGE_SIZE should not be used because it could
> > >>>>> be undefined or it could be defined differently on different operating
> > >>>>> systems.
> > >>>>>
> > >>>>> Stefano Stabellini (2):
> > >>>>>       usbif.h: replace PAGE_SIZE with USBIF_RING_SIZE
> > >>>>>       vscsiif.h: replace PAGE_SIZE with VSCSIIF_PAGE_SIZE
> > >>>>>
> > >>>>>  xen/include/public/io/usbif.h   | 5 +++--
> > >>>>>  xen/include/public/io/vscsiif.h | 3 ++-
> > >>>>>  2 files changed, 5 insertions(+), 3 deletions(-)
> > >>>>>
> > >>>> In principle I'm okay with these changes. But wouldn't it be
> > >>>> better to add
> > >>>>
> > >>>> #define XEN_RING_PAGE_SIZE 4096
> > >>>>
> > >>>> to xen/include/public/io/ring.h instead of having each interface
> > >>>> file its own definition?
> > >>> I would prefer to avoid having to spell out the page size for all the io
> > >>> interfaces, because the same interfaces should work fine with other page
> > >>> granularities, if the grant table hypercalls supported them.
> > >>>
> > >>> However in reality frontend and backend would have to agree on the page
> > >>> granularity to use beforehand. Some sort of consensus protocol is
> > >>> required. When that protocol is introduced, we could get rid of
> > >>> #define XEN_RING_PAGE_SIZE 4096.
> > >>>
> > >>> What do people think about this?
> > >> Not all current rings are 4k in size, and not all future rings should be
> > >> implicitly restricted to 4k.
> > >>
> > >> -1 to this introducing XEN_RING_PAGE_SIZE.  It will be more confusing
> > >> than helpful.
> > > Indeed, you are right. Since you are at it, feel like acking the current
> > > patches? :-)
> > 
> > Good point.  Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>,
> > although you also need a release ack at this point.
> > 
> 
> Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> 
> And applied.

Thanks. Please backport to stable trees.

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