Re: [Xen-devel] [RFC 08/16] xen/arm: p2m: Handle translation fault in get_page_from_gva

[Julien Grall <julien.grall@xxxxxxx>]

On 30/10/2018 00:47, Stefano Stabellini wrote:
> On Mon, 8 Oct 2018, Julien Grall wrote:
> > +            return NULL;
> > +        }
> > +
> > +        /*
> > +         * Check permission that are assumed by the caller. For instance
> > +         * in case of guestcopy, the caller assumes that the translated
> > +         * page can be accessed with the requested permissions. If this
> > +         * is not the case, we should fail.
> > +         *
> > +         * Please note that we do not check for the GV2M_EXEC
> > +         * permission. This is fine because the hardware-based translation
> > +         * instruction does not test for execute permissions.
> > +         */
> > +        if ( (flags & GV2M_WRITE) && !(perms & GV2M_WRITE) )
> > +            return NULL;
> > +
> > +        mfn = p2m_lookup(d, gaddr_to_gfn(ipa), &t);
> > +        if ( mfn_eq(INVALID_MFN, mfn) )
> > +            return NULL;
> > +
> > +        /* We consider that RAM is always mapped read-write */
> Is the RW assumption required? I can think of a case where RAM is mapped
> RO at stage2.
Just laziness for a first implementation. I will see how I can fix it.

> >       }
> > +    else
> > +        mfn = maddr_to_mfn(maddr);
> >   
> > -    if ( !mfn_valid(maddr_to_mfn(maddr)) )
> > +    if ( !mfn_valid(mfn) )
> >       {
> >           dprintk(XENLOG_G_DEBUG, "%pv: Invalid MFN %#"PRI_mfn"\n",
> > -                v, mfn_x(maddr_to_mfn(maddr)));
> > +                v, mfn_x(mfn));
> >           return NULL;
> >       }
> >   
> > -    page = mfn_to_page(maddr_to_mfn(maddr));
> > +    page = mfn_to_page(mfn);
> >       ASSERT(page);
> >   
> >       if ( unlikely(!get_page(page, d)) )
> > --
> > 2.11.0
Cheers,

--
Julien Grall

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