Re: [Xen-devel] [PATCH 2/3] Rename p2m_mmio_write_dm to p2m_ioreq_server

["Yu, Zhang" <yu.c.zhang@xxxxxxxxxxxxxxx>]

On 3/22/2016 10:15 PM, George Dunlap wrote:
> On 16/03/16 12:21, Yu Zhang wrote:
> > Previously p2m type p2m_mmio_write_dm was introduced for write-
> > protected memory pages whose write operations are supposed to be
> > forwarded to and emulated by an ioreq server. Yet limitations of
> > rangeset restricts the number of guest pages to be write-protected.
> >
> > This patch replace the p2m type p2m_mmio_write_dm with a new name:
> > p2m_ioreq_server, which means this p2m type can be claimed by one
> > ioreq server, instead of being tracked inside the rangeset of ioreq
> > server. Patches following up will add the related hvmop handling
> > code which maps type p2m_ioreq_server to an ioreq server.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> > ---
> [snip]
>
> > @@ -174,7 +174,8 @@ typedef unsigned int p2m_query_t;
> >
> >   #define p2m_is_any_ram(_t)  (p2m_to_mask(_t) &                   \
> >                                (P2M_RAM_TYPES | P2M_GRANT_TYPES |  \
> > -                              p2m_to_mask(p2m_map_foreign)))
> > +                              p2m_to_mask(p2m_map_foreign) | \
> > +                              p2m_to_mask(p2m_ioreq_server)))
> So this is the only bit that doesn't seem to be a straight rename.
> What's the rationale for adding this in this patch?
>
> And in any case, we want to add this to P2M_RAM_TYPES, don't we, so that
> p2m_is_ram() returns true?
>
> For example, if p2m_ioreq_server is *not* marked as p2m_is_ram(), then
> when it's ballooned out the m2p mapping won't be updated properly (see
> xen/arch/x86/mm/p2m.c:set_typed_p2m_entry()); and it looks like there
> could be issues with emulation when running in shadow mode (see
> xen/arch/x86/mm/common.c:emulate_gva_to_mfn()).  Other examples of this
> sort of thing abound.
Thank you, George. I now believe the right place we add p2m_ioreq_server
is in the P2M_RAM_TYPES. :)

> Everything else looks fine to me.
>
>   -George
B.R.
Yu

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