Re: [Xen-devel] [PATCH for-4.10 2/2] xen/arm: p2m: Add more debug in get_page_from_gva

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 16 Nov 2017, Julien Grall wrote:
> On 11/16/2017 01:36 AM, Stefano Stabellini wrote:
> > On Wed, 15 Nov 2017, Julien Grall wrote:
> > > The function get_page_from_gva is used by copy_*_guest helpers to
> > > translate a guest virtual address to a machine physical address and take
> > > reference on the page.
> > > 
> > > There are a couple of errors path that will return the same value making
> >                                 ^ paths
> > 
> > > difficult to know the exact error. Add more debug in each error patch
> > ^ it difficult
> > 
> > 
> > > only for debug-build.
> > > 
> > > This should help narrowing down the intermittent failure with the
> > > hypercall GNTTABOP_copy (see [1]).
> > > 
> > > [1] https://lists.xen.org/archives/html/xen-devel/2017-11/msg00942.html
> > > 
> > > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > 
> > Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > 
> > fixed on commit
> 
> I am not sure why this was merged given Andrew gave some comments...

Sorry Andrew! I missed your reply!

 
> > 
> > > ---
> > >   xen/arch/arm/p2m.c | 13 +++++++++++++
> > >   1 file changed, 13 insertions(+)
> > > 
> > > diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> > > index f6b3d8e421..417609ede2 100644
> > > --- a/xen/arch/arm/p2m.c
> > > +++ b/xen/arch/arm/p2m.c
> > > @@ -1428,16 +1428,29 @@ struct page_info *get_page_from_gva(struct vcpu
> > > *v, vaddr_t va,
> > >       par = gvirt_to_maddr(va, &maddr, flags);
> > >         if ( par )
> > > +    {
> > > +        dprintk(XENLOG_G_DEBUG,
> > > +                "%pv: gvirt_to_maddr failed va=%#"PRIvaddr" flags=0x%lx
> > > par=%#"PRIx64"\n",
> > > +                v, va, flags, par);
> > >           goto err;
> > > +    }
> > >         if ( !mfn_valid(maddr_to_mfn(maddr)) )
> > > +    {
> > > +        dprintk(XENLOG_G_DEBUG, "%pv: Invalid MFN %#"PRI_mfn"\n",
> > > +                v, mfn_x(maddr_to_mfn(maddr)));
> > >           goto err;
> > > +    }
> > >         page = mfn_to_page(maddr_to_mfn(maddr));
> > >       ASSERT(page);
> > >         if ( unlikely(!get_page(page, d)) )
> > > +    {
> > > +        dprintk(XENLOG_G_DEBUG, "%pv: Failing to acquire the MFN
> > > %#"PRI_mfn"\n",
> > > +                v, mfn_x(maddr_to_mfn(maddr)));
> > >           page = NULL;
> > > +    }
> > >     err:
> > >       if ( !page && p2m->mem_access_enabled )
> 

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