[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v6 4/4] x86/ioreq server: Reset outstanding p2m_ioreq_server entries when an ioreq server unmaps.





On 9/9/2016 5:44 PM, Jan Beulich wrote:
On 09.09.16 at 11:24, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
On 9/9/2016 4:20 PM, Jan Beulich wrote:
On 09.09.16 at 09:24, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
On 9/9/2016 1:26 PM, Yu Zhang wrote:
On 02.09.16 at 12:47, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
@@ -965,7 +968,8 @@ static mfn_t ept_get_entry(struct p2m_domain *p2m,
       if ( is_epte_valid(ept_entry) )
       {
           if ( (recalc || ept_entry->recalc) &&
-             p2m_is_changeable(ept_entry->sa_p2mt) )
+             p2m_is_changeable(ept_entry->sa_p2mt) &&
+             (ept_entry->sa_p2mt != p2m_ioreq_server) )
               *t = p2m_is_logdirty_range(p2m, gfn, gfn) ?
p2m_ram_logdirty
                                                         : p2m_ram_rw;
           else
Considering this (and at least one more similar adjustment further
down), is it really appropriate to include p2m_ioreq_server in the
set of "changeable" types?
Well, I agree p2m_ioreq_server do have different behaviors than the
p2m_log_dirty, but removing p2m_ioreq_server from changeable type
would need more specific code for the p2m_ioreq_server in routines like
resolve_misconfig(), do_recalc() and p2m_change_entry_type_global() etc.
I've tried this approach and abandoned later. :)
I can see that the other option might require more adjustments, in
which case I guess this variant would be fine if you created another
helper (well named) inline function instead of open coding this in
several places. Of course such dissimilar handling in the various
places p2m_is_changeable() gets used right now will additionally
require good reasoning - after all that predicate exists to express
the similarities between different code paths.
Thanks Jan.
Well, for the logic of p2m type recalculation, similarities between
p2m_ioreq_server
and other changeable types exceeds their differences. As to the special
cases, how
about we use a macro, i.e. p2m_is_ioreq?
That'd be better than the open coded check, but would still result
in (taking the above example)

              p2m_is_changeable(ept_entry->sa_p2mt) &&
              !p2m_is_ioreq(ept_entry->sa_p2mt) )

? What I'd prefer is a predicate that can be applied here on its own,
without involving && or ||.


OK. I can think of 2 scenarios that p2m_ioreq_server needs special handling:

1> In ept_get_entry()/recal_type(), the p2m types are supposed to return as it is, instead of changing to p2m_log_dirty. So we can use a macro or a inline function like p2m_check_changeable(),
which combines the

             p2m_is_changeable(ept_entry->sa_p2mt) &&
             !p2m_is_ioreq(ept_entry->sa_p2mt) )

together.

2> In resolve_misconfig()/do_recalc(), the entry_count gets decremented. We
do not need this new inline function, because they are in a separate if() statement.

Is this OK? :)

Thanks
Yu



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.