[libvirt] [PATCH 1/2] qemu: Add capability flag for usb-storage

[Daniel P. Berrange]

On Tue, Aug 13, 2013 at 01:52:33PM +0200, Fred A. Kemp wrote:
> From: "Fred A. Kemp" <anonym at riseup.net>
> 
> Allow use of the usb-storage device only if the new capability flag
> QEMU_CAPS_DEVICE_USB_STORAGE is set, which it is for qemu(-kvm)
> versions >= 0.12.1.2-rhel62-beta.
> ---
>  src/qemu/qemu_capabilities.c |    2 ++
>  src/qemu/qemu_capabilities.h |    1 +
>  src/qemu/qemu_command.c      |    6 +++---
>  tests/qemuhelptest.c         |   18 ++++++++++++------
>  tests/qemuxml2argvtest.c     |    3 ++-
>  5 files changed, 20 insertions(+), 10 deletions(-)
> 
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index 47cc07a..5c566c1 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -235,6 +235,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
>                "vnc-share-policy", /* 150 */
>                "device-del-event",
>                "dmi-to-pci-bridge",
> +              "usb-storage",
>      );
>  
>  struct _virQEMUCaps {
> @@ -1383,6 +1384,7 @@ struct virQEMUCapsStringFlags virQEMUCapsObjectTypes[] = {
>      { "vfio-pci", QEMU_CAPS_DEVICE_VFIO_PCI },
>      { "scsi-generic", QEMU_CAPS_DEVICE_SCSI_GENERIC },
>      { "i82801b11-bridge", QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE },
> +    { "usb-storage", QEMU_CAPS_DEVICE_USB_STORAGE },
>  };
>  
>  static struct virQEMUCapsStringFlags virQEMUCapsObjectPropsVirtioBlk[] = {
> diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
> index 074e55d..4a8b14b 100644
> --- a/src/qemu/qemu_capabilities.h
> +++ b/src/qemu/qemu_capabilities.h
> @@ -191,6 +191,7 @@ enum virQEMUCapsFlags {
>      QEMU_CAPS_VNC_SHARE_POLICY   = 150, /* set display sharing policy */
>      QEMU_CAPS_DEVICE_DEL_EVENT   = 151, /* DEVICE_DELETED event */
>      QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE  = 152, /* -device i82801b11-bridge */
> +    QEMU_CAPS_DEVICE_USB_STORAGE = 153, /* -device usb-storage */
>  
>      QEMU_CAPS_LAST,                   /* this must always be the last item */
>  };
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index b811e1d..03fb798 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -8044,10 +8044,10 @@ qemuBuildCommandLine(virConnectPtr conn,
>              bool withDeviceArg = false;
>              bool deviceFlagMasked = false;
>  
> -            /* Unless we have -device, then USB disks need special
> -               handling */
> +            /* Unless we have `-device usb-storage`, then USB disks
> +               need special handling */
>              if ((disk->bus == VIR_DOMAIN_DISK_BUS_USB) &&
> -                !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
> +                !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_USB_STORAGE)) {
>                  if (disk->device == VIR_DOMAIN_DISK_DEVICE_DISK) {
>                      virCommandAddArg(cmd, "-usbdevice");
>                      virCommandAddArgFormat(cmd, "disk:%s", disk->src);

Hmm, I'm not sure this logic change is right.

Previously if you have -device support, but 'usb-storage' was not
available, libvirt would try to start the guest with -device & then
QEMU would report an error.

With this change, if you have -device support, but 'usb-storage' was
not available, then libvirt is going to fallback to using the legacy
'-usbdevice' support. This is not good.

Adding an explicit check for 'usb-storage' is a fine goal, but we
should be doing that check in the branch of this  if() that handles
'-device usb-storage', so we don't exercise the -usbdevice branch


Daniel
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