Re: [Xen-devel] [PATCH v2 1/2] Resize the MAX_NR_IO_RANGES for ioreq server

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 07 July 2015 16:27
> To: Paul Durrant
> Cc: Andrew Cooper; George Dunlap; Kevin Tian; zhiyuan.lv@xxxxxxxxx; Zhang
> Yu; xen-devel@xxxxxxxxxxxxx; Keir (Xen.org)
> Subject: RE: [Xen-devel] [PATCH v2 1/2] Resize the MAX_NR_IO_RANGES for
> ioreq server
> 
> >>> On 07.07.15 at 17:12, <Paul.Durrant@xxxxxxxxxx> wrote:
> > I don't think that the Xan parts of XenGT are that far off. I had a list of
> > 3 items:
> >
> > - 16 byte I/O brokenness, which should be fixed now
> > - Basic PV-IOMMU implementation, which I think Malcolm should be
> posting very soon
> 
> No matter how soon Malcolm would post that, unless it is in a shape
> to go in without any revisions, it will - afaict - miss 4.6 (freezing at
> the end of the week). I can't even guarantee that your HVM
> emulation updates will have gone in by then, but I very much hope
> so.
> 
> > - Shadow GTT emulation (which is what we're looking at here)
> >
> > I had a chat with George earlier and wondered whether we might approach
> > things this way:
> >
> > - Add a new sub op to HVMOP_[un]map_io_range_to_ioreq_server or a
> new
> > HVM_[un]map_gfn_to_ioreq_server
> > - Make rb_rangeset the default rangeset implementation (since I believe it
> > can only be an improvement even if it makes no significant difference for
> > small numbers of ranges)
> > - Use a common implementation for MMIO ranges and GFN ranges *for
> now* (which
> > does mean increasing the limit) to allow us to be functionally complete for
> > 4.6
> > - Follow up (post-4.6) with a different ioreq server redirection
> > implementation for mmio-dm and mmio-dm-write pages, possibly based
> on claiming a
> > range of page types for emulator use, to optimize shadow GTT
> implementation.
> >
> > Does that sound plausible?
> 
> Yes, except that I think all of this will be post-4.6.
> 

Ok, if we miss 4.6 then so be it, but we'll go with that plan and live in hope 
;-)

  Paul

> Jan


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