Re: [Xen-devel] [PATCH 6/8] xen/arm: Retrieve p2m type in get_page_from_gfn

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 12/05/2013 04:23 PM, Ian Campbell wrote:
> On Thu, 2013-12-05 at 15:42 +0000, Julien Grall wrote:
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > ---
> >   xen/include/asm-arm/p2m.h |    5 ++---
> >   1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
> > index 3de69c4..54d1dab 100644
> > --- a/xen/include/asm-arm/p2m.h
> > +++ b/xen/include/asm-arm/p2m.h
> > @@ -105,9 +105,8 @@ static inline struct page_info *get_page_from_gfn(
> >       struct domain *d, unsigned long gfn, p2m_type_t *t, p2m_query_t q)
> >   {
> >       struct page_info *page;
> > -    unsigned long mfn = gmfn_to_mfn(d, gfn);
> > -
> > -    ASSERT(t == NULL);
> > +    paddr_t maddr = p2m_get_entry(d, pfn_to_paddr(gfn), t);
> > +    unsigned long mfn = maddr >> PAGE_SHIFT;
> Do we need to eg. convert p2m_invalid into returning NULL instead of
> whatever maddr contains in that case?
In that case maddr will contain INVALID_PADDR, which will turn in 
INVALID_MFN with the shift. So we don't need to check the p2m type.
> In the case of p2m_mmio_direct we need to be careful because there is no
> struct page. Ah.. here it is in the context:
> >       if (!mfn_valid(mfn))
> >           return NULL;
> Although I wonder if we should convert mmio_direct into NULL even if the
> MMIO region happens to have a struct page? (e.g. due to holes in the
> frametable)
Actually, I think it's fine. get_page will fail because the page won't 
belong to the domain. So the function will return NULL.
--
Julien Grall

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