Re: [PATCH V2] Xen: ARM: Zero reserved fields of xatp before making hypervisor call

[Julien Grall]

Hi Stefano,

On 03/01/17 18:03, Stefano Stabellini wrote:
> On Mon, 2 Jan 2017, Juergen Gross wrote:
> > On 28/12/16 01:47, Jiandi An wrote:
> > > Ensure all reserved fields of xatp are zero before making
> > > hypervisor call to XEN in xen_map_device_mmio().
> > > xenmem_add_to_physmap_one() in XEN fails the mapping request if
> > > extra.res reserved field in xatp is not zero for XENMAPSPACE_dev_mmio
> > > request.
> > >
> > > Signed-off-by: Jiandi An <anjiandi@xxxxxxxxxxxxxx>
> > > ---
> > > Changed zeroing xatp to a static initialization
> > > of .domid and .space for xatp.
> > >
> > >  drivers/xen/arm-device.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/xen/arm-device.c b/drivers/xen/arm-device.c
> > > index 778acf8..85dd20e 100644
> > > --- a/drivers/xen/arm-device.c
> > > +++ b/drivers/xen/arm-device.c
> > > @@ -58,9 +58,13 @@ static int xen_map_device_mmio(const struct resource *resources,
> > >  	xen_pfn_t *gpfns;
> > >  	xen_ulong_t *idxs;
> > >  	int *errs;
> > > -	struct xen_add_to_physmap_range xatp;
> > >
> > >  	for (i = 0; i < count; i++) {
> > > +		struct xen_add_to_physmap_range xatp = {
> > > +			.domid = DOMID_SELF,
> > > +			.space = XENMAPSPACE_dev_mmio
> > > +		};
> > > +
> >
> > I still don't see the need to re-initialize the input parts of xatp
> > on each loop iteration unless you can show the need for it (e.g. a
> > buggy hypervisor version not conforming to the interface specification).
> >
> > OTOH I don't feel really strong about it and let Stefano being the
> > maintainer for the ARM parts decide.
>
> I don't feel strongly about this either - I think this patch is good
> enough. I'll apply to xentip.

I think this patch should be backported to stable trees because the 
issue could appear depending on the compiler.

Cheers,

--
Julien Grall