> -----Original Message-----
> From: Roger Pau Monne <roger....@citrix.com>
> Sent: 22 August 2019 08:41
> To: Paul Durrant <paul.durr...@citrix.com>
> Cc: xen-devel@lists.xenproject.org; Jan Beulich <jbeul...@suse.com>; Andrew
> Cooper
> <andrew.coop...@citrix.com>; Wei Liu <w...@xen.org>
> Subject: Re: [PATCH 3/7] ioreq: allow dispatching ioreqs to internal servers
>
> 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.
Exactly what I was thinking.
>
> 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.
>
I'd not considered a union, but it makes sense :-)
Paul
> Thanks, Roger.
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