Re: [Xen-devel] [PATCH 1/4] move XENMEM_add_to_physmap handling framework to common code

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2013-12-20 at 09:12 +0000, Jan Beulich wrote:
> >>> On 20.12.13 at 09:58, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > On Fri, 2013-12-20 at 07:48 +0000, Jan Beulich wrote:
> >> >>> On 18.12.13 at 18:52, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> >> > On Wed, 2013-12-18 at 14:34 +0000, Jan Beulich wrote:
> >> >> There's really nothing really architecture specific here; the
> >> >> architecture specific handling is limited to
> >> >> xenmem_add_to_physmap_one().
> >> >> 
> >> >> Note that ARM's restriction of XENMAPSPACE_gmfn_foreign only being
> >> >> supported through XENMEM_add_to_physmap_range is being dropped as being
> >> >> pointless.
> >> > 
> >> > It's not pointless, dropping this restriction turns a comprehensible
> >> > EINVAL result into an incorrect ESRCH result. Which is incorrect because
> >> > no domain was specified so how can it not exist.
> >> 
> >> How can there have been no domain specified for a
> >> XENMAPSPACE_gmfn_foreign?
> > 
> > The arguments to XENMEM_add_to_physmap have no field which specifies a
> > foreign domain. (this is one of the reasons we added the _range version
> > with the field in the first place).
> > 
> > The domid parameter to add_to_physmap one is why hardcoded to
> > DOMID_INVALID in all the add_to_physmap (!range) cases.
> > 
> >>  If the field was left uninitialized,
> >> -ESRCH would be as valid as -EINVAL, and I don't think we
> >> specify for any hypercall that between multiple applicable
> >> error code a specific one would be preferred over others.
> > 
> > I think given the above -ESRCH is invalid, since there is no field to
> > have been left uninitialised.
> 
> Oh, I finally understand. The thing that mainly confused me here
> is the wording of the original comment: "Foreign mapping is only
> supported by add_to_physmap_range". Whereas it should have
> said "Foreign mapping is only possible through
> add_to_physmap_range". I'll re-add that with the adjusted
> comment.

Yes, thanks.

> Will that make the patch acceptable to you?

I believe so, yes, I'll look at v3 ASAP.

Ian.


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