On Wed, Aug 21, 2019 at 06:29:04PM +0200, Paul Durrant wrote:
> > -----Original Message-----
> > From: Roger Pau Monne <roger....@citrix.com>
> > Sent: 21 August 2019 15:59
> > To: xen-devel@lists.xenproject.org
> > Cc: Roger Pau Monne <roger....@citrix.com>; Paul Durrant
> > <paul.durr...@citrix.com>; Jan Beulich
> > <jbeul...@suse.com>; Andrew Cooper <andrew.coop...@citrix.com>; Wei Liu
> > <w...@xen.org>
> > Subject: [PATCH 3/7] ioreq: allow dispatching ioreqs to internal servers
> >
> > Internal ioreq servers are always processed first, and ioreqs are
> > dispatched by calling the handler function. If no internal servers have
> > registered for an ioreq it's then forwarded to external callers.
>
> Distinct id ranges would help here... Internal ids could be walked first,
> then external. If there's no possibility of interleaving then you don't need
> the retry.
So if internal vs external is keyed on the ID then we would end up
with two different arrays in hvm_domain, one for internal and one for
external ioreq servers.
Maybe instead of my previous suggestion it would be better to just
define consecutive ranges for external and internal servers, like:
#define MAX_NR_EXTERNAL_IOREQ_SERVERS 8
#define MAX_NR_INTERNAL_IOREQ_SERVERS 1
#define MAX_NR_IOREQ_SERVERS \
(MAX_NR_EXTERNAL_IOREQ_SERVERS + MAX_NR_INTERNAL_IOREQ_SERVERS)
#define FOR_EACH_IOREQ_SERVER(d, id, s) \
for ( (id) = MAX_NR_IOREQ_SERVERS * 2; (id) != 0; ) \
if ( !(s = GET_IOREQ_SERVER(d, --(id))) ) \
continue; \
else
#define FOR_EACH_INTERNAL_IOREQ_SERVER(d, id, s) \
for ( (id) = MAX_NR_IOREQ_SERVERS; (id) > MAX_NR_INTERNAL_IOREQ_SERVERS &&
(id) != 0; ) \
if ( !(s = GET_IOREQ_SERVER(d, --(id))) ) \
continue; \
else
#define FOR_EACH_EXTERNAL_IOREQ_SERVER(d, id, s) \
for ( (id) = MAX_NR_INTERNAL_IOREQ_SERVERS; (id) != 0; ) \
if ( !(s = GET_IOREQ_SERVER(d, --(id))) ) \
continue; \
else
That would also force FOR_EACH_IOREQ_SERVER to always process internal
ioreq servers first.
We could even have something like:
union {
struct {
struct hvm_ioreq_server *external_server[MAX_NR_EXTERNAL_IOREQ_SERVERS];
struct hvm_ioreq_server *internal_server[MAX_NR_INTERNAL_IOREQ_SERVERS];
}
struct hvm_ioreq_server *server[MAX_NR_IOREQ_SERVERS];
}
In order to split the arrays if required.
Thanks, Roger.
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