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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 4 Aug 2014, Vijay Kilari wrote:
> On Wed, Jul 16, 2014 at 6:18 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> > 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.
> 
> Thank Ian.
> 
> I have another query
> 
> Scenario:
> 
> DOM0 allocates a page for LPI configuration and write start address of
> this page (IPA)
> is written to register PROP_BASER. which is trapped.
> Now DOM0 uses this allocated page to configure LPI's, which is not trapped.
> 
> I want to trap on any writes to this page. so that LPI's can be
> enabled/disabled.
> Is there any API in Xen to unmap Dom's page so that Xen can get trap
> on read/writes
> to this page ?

Usually these pages are part of an MMIO region that is not mapped in the
first place.

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