Re: [Qemu-devel] [PATCH] add pci-bridge-seat

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Mar 16, 2015 at 11:36:43AM +0100, Gerd Hoffmann wrote:
> Simplifies multiseat configuration, see
> docs/multiseat.txt update for details.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  docs/multiseat.txt             | 19 +++++++++++++++++++
>  docs/specs/pci-ids.txt         |  1 +
>  hw/pci-bridge/pci_bridge_dev.c | 25 ++++++++++++++++++++++++-
>  include/hw/pci/pci.h           |  1 +
>  4 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/multiseat.txt b/docs/multiseat.txt
> index b963665..814496e 100644
> --- a/docs/multiseat.txt
> +++ b/docs/multiseat.txt
> @@ -106,6 +106,25 @@ the devices attached to the seat.
>  Background info is here:
>    http://www.freedesktop.org/wiki/Software/systemd/multiseat/
>  
> +
> +guest side with pci-bridge-seat
> +-------------------------------
> +
> +Qemu version FIXME and newer has a new pci-bridge-seat device which
> +can be used instead of pci-bridge.  Just swap the device name in the
> +qemu command line above.  The only difference between the two devices
> +is the pci id.  We can match the pci id instead of the device path
> +with a nice generic rule now, which simplifies the guest
> +configuration:
> +
> +    [root@fedora ~]# cat /etc/udev/rules.d/70-qemu-pci-bridge-seat.rules
> +    SUBSYSTEM=="pci", ATTR{vendor}=="0x1b36", ATTR{device}=="0x000a", \
> +            TAG+="seat", ENV{ID_AUTOSEAT}="1"
> +
> +Patch with this rule will be submitted to upstream udev/systemd, so
> +long-term, when systemd with this lands in distros, things will work
> +just fine without any manual guest configuration.
> +
>  Enjoy!
>  

I'm confused. What's wrong with using the regular bridge,
and ATTR{vendor}=="0x1b36", ATTR{device}=="0x0001"?


>  --
> diff --git a/docs/specs/pci-ids.txt b/docs/specs/pci-ids.txt
> index c6732fe..cdeb805 100644
> --- a/docs/specs/pci-ids.txt
> +++ b/docs/specs/pci-ids.txt
> @@ -46,6 +46,7 @@ PCI devices (other than virtio):
>  1b36:0004  PCI Quad-port 16550A adapter (docs/specs/pci-serial.txt)
>  1b36:0005  PCI test device (docs/specs/pci-testdev.txt)
>  1b36:0007  PCI SD Card Host Controller Interface (SDHCI)
> +1b36:000a  PCI-PCI bridge (multiseat)
>  
>  All these devices are documented in docs/specs.
>  
> diff --git a/hw/pci-bridge/pci_bridge_dev.c b/hw/pci-bridge/pci_bridge_dev.c
> index 36f73e1..e966d2e 100644
> --- a/hw/pci-bridge/pci_bridge_dev.c
> +++ b/hw/pci-bridge/pci_bridge_dev.c
> @@ -28,7 +28,8 @@
>  #include "hw/pci/pci_bus.h"
>  #include "hw/hotplug.h"
>  
> -#define TYPE_PCI_BRIDGE_DEV "pci-bridge"
> +#define TYPE_PCI_BRIDGE_DEV      "pci-bridge"
> +#define TYPE_PCI_BRIDGE_SEAT_DEV "pci-bridge-seat"
>  #define PCI_BRIDGE_DEV(obj) \
>      OBJECT_CHECK(PCIBridgeDev, (obj), TYPE_PCI_BRIDGE_DEV)
>  
> @@ -170,9 +171,31 @@ static const TypeInfo pci_bridge_dev_info = {
>      }
>  };
>  
> +/*
> + * Multiseat bridge.  Same as the standard pci bridge, only with a
> + * different pci id, so we can match it easily in the guest for
> + * automagic multiseat configuration.  See docs/multiseat.txt for more.

Hmm, this doesn't give me any info except it has something
to do with multiseat (which is itself an ambigious term)
and is somehow magic.

It's probably obvious to you - maybe you can explain?

> + */
> +static void pci_bridge_dev_seat_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
> +
> +    k->device_id = PCI_DEVICE_ID_REDHAT_BRIDGE_SEAT;
> +    dc->desc = "Standard PCI Bridge (multiseat)";
> +}
> +
> +static const TypeInfo pci_bridge_dev_seat_info = {
> +    .name              = TYPE_PCI_BRIDGE_SEAT_DEV,
> +    .parent            = TYPE_PCI_BRIDGE_DEV,
> +    .instance_size     = sizeof(PCIBridgeDev),
> +    .class_init        = pci_bridge_dev_seat_class_init,
> +};
> +
>  static void pci_bridge_dev_register(void)
>  {
>      type_register_static(&pci_bridge_dev_info);
> +    type_register_static(&pci_bridge_dev_seat_info);
>  }
>  
>  type_init(pci_bridge_dev_register);
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index be2d9b8..320c389 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -90,6 +90,7 @@
>  #define PCI_DEVICE_ID_REDHAT_TEST        0x0005
>  #define PCI_DEVICE_ID_REDHAT_SDHCI       0x0007
>  #define PCI_DEVICE_ID_REDHAT_PCIE_HOST   0x0008
> +#define PCI_DEVICE_ID_REDHAT_BRIDGE_SEAT 0x000a
>  #define PCI_DEVICE_ID_REDHAT_QXL         0x0100
>  
>  #define FMT_PCIBUS                      PRIx64
> -- 
> 1.8.3.1