Re: [Xen-devel] [PATCH 7/7] ioreq: provide support for long-running operations...

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Roger Pau Monne <roger.pau@citrix.com>
> Sent: 22 August 2019 13:55
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: xen-devel@lists.xenproject.org; Jan Beulich <jbeulich@suse.com>; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; Wei Liu <wl@xen.org>; George Dunlap <George.Dunlap@citrix.com>; Ian
> Jackson <Ian.Jackson@citrix.com>; Julien Grall <julien.grall@arm.com>; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; Stefano Stabellini <sstabellini@kernel.org>; Tim (Xen.org) <tim@xen.org>
> Subject: Re: [PATCH 7/7] ioreq: provide support for long-running operations...
> 
> On Thu, Aug 22, 2019 at 11:15:50AM +0200, Paul Durrant wrote:
> > > -----Original Message-----
> > > From: Roger Pau Monne <roger.pau@citrix.com>
> > > Sent: 21 August 2019 15:59
> > > To: xen-devel@lists.xenproject.org
> > > Cc: Roger Pau Monne <roger.pau@citrix.com>; Paul Durrant <Paul.Durrant@citrix.com>; Jan Beulich
> > > <jbeulich@suse.com>; Andrew Cooper <Andrew.Cooper3@citrix.com>; Wei Liu <wl@xen.org>; George
> Dunlap
> > > <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Julien Grall
> <julien.grall@arm.com>;
> > > Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>; Stefano Stabellini <sstabellini@kernel.org>; Tim
> > > (Xen.org) <tim@xen.org>
> > > Subject: [PATCH 7/7] ioreq: provide support for long-running operations...
> > >
> > > ...and switch vPCI to use this infrastructure for long running
> > > physmap modification operations.
> > >
> > > This allows to get rid of the vPCI specific modifications done to
> > > handle_hvm_io_completion and allows generalizing the support for
> > > long-running operations to other internal ioreq servers. Such support
> > > is implemented as a specific handler that can be registers by internal
> > > ioreq servers and that will be called to check for pending work.
> > > Returning true from this handler will prevent the vcpu from running
> > > until the handler returns false.
> >
> > Rather than having another callback can the handler not be re-called with same ioreq? It could
> return different values depending on whether there is more work to do (requiring another call) or
> whether it is done and the vcpu can be resumed. Would that work?
> 
> I guess this would work also. The issue with this approach is that I
> would have to find somewhere to store the ioreq while the operation is
> being processed, which is not required with the proposed two handler
> approach.

The ioreq already is stored in v->arch.hvm.hvm_io.io_req anyway, so can't you use that copy?

  Paul

> 
> Thanks, Roger.

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