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Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support
From: |
Alex Williamson |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support |
Date: |
Wed, 12 Sep 2018 11:13:54 -0600 |
On Tue, 11 Sep 2018 06:38:43 +0200
Gerd Hoffmann <address@hidden> wrote:
> Hi,
>
> > > type_register_static(&vfio_pci_dev_info);
> > > + type_register_static(&vfio_pci_ramfb_dev_info);
>
> > My concern here is still all of the extra tooling that needs to be
> > added to management layers above QEMU for this device that exists only
> > because we can't hotplug the primary display in QEMU. What happens when
> > we can hotplug the primary display?
>
> Ramfb uses fw_cfg, and fw_cfg files can't be added or removed at
> runtime, the interface simply isn't designed for that.
>
> > Aren't disabling hotplug of a
> > vfio-pci device and supporting ramfb two separate things? I think
> > we're leaking current implementation issues out to the device options
> > when really we'd rather have a "ramfb" (or perhaps "console") option on
> > the vfio-pci device and the hotplug capability determined automatically
> > and available through introspection of the device.
>
> Well, I don't think libvirt will have too much trouble handling this.
> We have two variants (with and without vga compatibility) of other
> devices: qxl-vga and qxl, virtio-vga and virtio-gpu-pci. libvirt copes
> just fine and picks the right one (I think depending on video model
> 'primary' property).
>
> Also libvirt manages hotpluggability per device *class*, not per device
> *instance*. So a device being hotpluggable or not depending on some
> device property is a problem for libvirt ...
>
> I'm open to suggestions how to handle this better, as long as the
> libvirt people are on board with the approach.
Ok, so we need a new class to handle making a device non-hotpluggable,
but I'm still not sure whether we should make:
-device vfio-pci-ramfb
or
-device vfio-pci-nohotplug,ramfb=on
Where ramfb would be a property only available on the nohotplug class
variant. The latter seems to provide a lot more flexibility, but which
is more practical for libvirt? Thanks,
Alex
- [Qemu-devel] [PATCH 0/2] hw/vfio/display: add ramfb support, Gerd Hoffmann, 2018/09/10
- [Qemu-devel] [PATCH 1/2] stubs: add ramfb, Gerd Hoffmann, 2018/09/10
- [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support, Gerd Hoffmann, 2018/09/10
- Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support, Alex Williamson, 2018/09/10
- Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support, Gerd Hoffmann, 2018/09/11
- Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support,
Alex Williamson <=
- Re: [Qemu-devel] [PATCH 2/2] hw/vfio/display: add ramfb support, Gerd Hoffmann, 2018/09/14
- Re: [Qemu-devel] [libvirt] [PATCH 2/2] hw/vfio/display: add ramfb support, Erik Skultety, 2018/09/14
- Re: [Qemu-devel] [libvirt] [PATCH 2/2] hw/vfio/display: add ramfb support, Alex Williamson, 2018/09/14
- Re: [Qemu-devel] [libvirt] [PATCH 2/2] hw/vfio/display: add ramfb support, Erik Skultety, 2018/09/18