Re: [Xen-devel] [PATCH 11/14] xen/x86: mm: Re-implement set_gpfn_from_mfn() as a static inline function

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 10/05/2019 14:48, Jan Beulich wrote:
> > > > On 10.05.19 at 15:41, <julien.grall@xxxxxxx> wrote:
> > On 10/05/2019 14:35, Jan Beulich wrote:
> > > > > > On 10.05.19 at 15:27, <julien.grall@xxxxxxx> wrote:
> > > > On 10/05/2019 13:43, Jan Beulich wrote:
> > > > > > > > On 07.05.19 at 17:14, <julien.grall@xxxxxxx> wrote:
> > > > > > +static inline void set_gpfn_from_mfn(unsigned long mfn, unsigned long pfn)
> > > > > > +{
> > > > > > +    struct domain *d = page_get_owner(mfn_to_page(_mfn(mfn)));
> > > > > > +    unsigned long entry = (d && (d == dom_cow)) ? SHARED_M2P_ENTRY : pfn;
> > > > > The && here looks, ehm, funny, but I guess it's needed for early boot?
> > > > I have no idea, this is x86 not Arm...
> > > >
> > > > > But that's perhaps a separate thing to clean up. However, looking at
> > > > > this - why is Arm setting up dom_cow in the first place?
> > > > Common code is using dom_cow, so I don't think we want it to be NULL on Arm to
> > > > avoid weird issues.
> > > I didn't mean it to remain NULL. Common code doesn't dereference it
> > > (and isn't supposed to), so I'd consider initializing it to some known
> > > faulting non-NULL address, if there is such on Arm.
> > Patches are welcomed ;).
> So is there such an address on Arm?
0 - 2MB is unmapped so far. I don't know whether this will still be the case (at 
least for the range 4KB - 2MB) with the rework I am attempting.
Cheers,

--
Julien Grall

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