Re: [libvirt] [RFC v2] libvirt vGPU QEMU integration

On Tue, 20 Sep 2016 02:05:52 +0530 Kirti Wankhede <kwankhede(a)nvidia.com&gt; wrote: > 'fb_length': > Read-only file. Mandatory. > Returns <number>{K,M,G}, size of framebuffer. This can't be mandatory, it's only relevant to vGPU devices, vGPUs are just one user of mediated devices. [...] > 'params' > Write-Only file. Optional. > String input. Libvirt would pass the string given in XML file to > this file and then create mdev device. Set empty string to clear params. > For example, set parameter 'frame_rate_limiter=0' to disable frame rate > limiter for performance benchmarking, then create device of type 11. The > device created would have that parameter set by vendor driver. Might as well just call it "magic", there's absolutely no ability to introspect what parameters are allowed or even valid here. Can all parameters be changed dynamically? Do parameter changes apply to existing devices or only future devices? This is a poorly specified interface. I'd prefer this be done via module options on the vendor driver.

> The parent device would look like: > > <device> > <name>pci_0000_86_00_0</name> > <capability type='pci'> > <domain>0</domain> > <bus>134</bus> > <slot>0</slot> > <function>0</function> This is the parent device address?

> 2. Create/destroy mediated device > > With above example, vGPU device XML would look like: > > <device> > <name>my-vgpu</name> > <parent>pci_0000_86_00_0</parent> > <capability type='mdev'> > <type id='11'/> > <group>1</group> > <params>'frame_rate_limiter=0'</params> > </capability> > </device> > > 'type id' is mandatory. I was under the impression that the vendor supplied "name" was the one unique identifier. We're certainly not going to create a registrar to hand out type ids to each vendor, so what makes type id unique?

> * Clear params, if set earlier: > > echo "" > /sys/../0000\:86\:00.0/11/params So params only applies to the devices created while those params are set? This is inherently racy.