Re: [Xen-devel] Xen/ARM: Xen queries

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-07-16 at 18:15 +0530, Vijay Kilari wrote:
> On Tue, Jul 15, 2014 at 2:16 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > On Tue, 2014-07-15 at 14:14 +0530, Vijay Kilari wrote:
> >> > BTW, is there any reason to not use copy_{from,to}_guest helpers?
> >>
> >>   What Xen has is IPA address of Command Queue. Can copy_{from,to}_guest()
> >> work with guest IPA address?
> >
> > No, they use guest VAs.
> >
> > That's not to say that some helpers for copying from guest IPA wouldn't
> > be a useful addition to Xen though.
> 
>    I understand that this helper uses map_domain_page() to do so.
> 
> Query: Is there any existing helpers to convert guest IPA to PA?. I want
> to access the physical address for a given IPA and program the device with PA.

You want p2m_lookup() which does IPA->MA translation. Or perhaps it
would be better/more convenient to get_page_from_gfn() which takes an
API and returns you the struct page_info * with the reference count
bumped.

Ian.


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