> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 04 February 2016 14:13 > To: Paul Durrant > Cc: Andrew Cooper; George Dunlap; Ian Campbell; Ian Jackson; Stefano > Stabellini; Wei Liu; Kevin Tian; zhiyuan...@intel.com; Zhang Yu; xen- > de...@lists.xen.org; Keir (Xen.org) > Subject: RE: [Xen-devel] [PATCH v3 3/3] tools: introduce parameter > max_wp_ram_ranges. > > >>> On 04.02.16 at 14:47, <paul.durr...@citrix.com> wrote: > >> From: Ian Jackson [mailto:ian.jack...@eu.citrix.com] > >> Sent: 04 February 2016 13:34 > >> * Is it possible for libxl to somehow tell from the rest of the > >> configuration that this larger limit should be applied ? > >> > >> AFAICT there is nothing in libxl directly involving vgpu. How can > >> libxl be used to create a guest with vgpu enabled ? I had thought > >> that this was done merely with the existing PCI passthrough > >> configuration, but it now seems that somehow a second device model > >> would have to be started. libxl doesn't have code to do that. > >> > > > > AIUI if the setting of the increased limit is tied to provisioning a gvt-g > > instance for a VM then I don't there needs to be extra information in the > VM > > config. These seems like the most sensible thing to do. > > I don't understand this: For one, it's still unclear to me on what basis > it would be known that a given VM is a "gvt-g instance". And even if > that's indeed derivable from something, the uncertainty about a > workable upper bound on the number of WP ranges would still seem > to demand the value to be specifiable separately...
There are patches in the XenGT xen repo which add extra parameters into the VM config to allow libxl to provision a gvt-g instance (of which there are a finite number per GPU) for a VM. The increased limit could be applied when doing so and it may be feasible to determine (maybe from the version of the GPU h/w) what a reasonable limit is. Paul > > >> I now understand that these mmio ranges are created by the device > >> model. Of course the device model needs to be able to create mmio > >> ranges for the guest. And since they consume hypervisor resources, > >> the number of these must be limited (device models not necessarily > >> being trusted). > > > > ...but I think there is still an open question as to whether the toolstack > > is allowed to set that limit for a VM or not. IMO the toolstack should be > > allowed to set that limit when creating a domain. > > ... as you indicate here. > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
