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Re: [libvirt] [PATCH] qemu: add the USB devices to the cgroup whitelist



On Sat, Oct 30, 2010 at 12:25:30AM +0200, Diego Elio Pettenò wrote:
> Add a new interface to hostusb.h to add an USB device abstraction to a
> cgroup whitelist; then use it both when attaching a new USB device and when
> adding it to the commandline so that the device can be accessed by the
> QEmu-specific cgroup.
> ---
>  src/libvirt_private.syms |    1 +
>  src/qemu/qemu_driver.c   |   36 ++++++++++++++++++++++++++++++++++++
>  src/util/hostusb.c       |    6 ++++++
>  src/util/hostusb.h       |    4 +++-
>  4 files changed, 46 insertions(+), 1 deletions(-)
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index cf06256..0c6f308 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -707,6 +707,7 @@ virMutexUnlock;
>  
>  
>  # usb.h
> +usbAllowDeviceCgroup;
>  usbDeviceFileIterate;
>  usbDeviceGetBus;
>  usbDeviceGetDevno;
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 1eea3a9..acf319e 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -3505,6 +3505,23 @@ static int qemuSetupCgroup(struct qemud_driver *driver,
>                                     qemuSetupChardevCgroup,
>                                     cgroup) < 0)
>              goto cleanup;
> +
> +        for (i = 0; i < vm->def->nhostdevs; i++) {
> +          virDomainHostdevDefPtr hostdev = vm->def->hostdevs[i];
> +          usbDevice *usb;
> +
> +          if (hostdev->mode != VIR_DOMAIN_HOSTDEV_MODE_SUBSYS)
> +            continue;
> +          if (hostdev->source.subsys.type != VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB)
> +            continue;
> +
> +          if ((usb = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
> +                                   hostdev->source.subsys.u.usb.product)) == NULL)
> +            goto cleanup;

This should actually use  usbGetDevice with bus+device, since the
(optional) vendor+product has already been resolved into a bus+device
ID pair.

> +          if (usbAllowDeviceCgroup(usb, cgroup) < 0)
> +            goto cleanup;
> +        }
>      }

This should call out to usbDeviceFileIterate, passing a callback
todo the cgroup relabelling.

>  
>      if ((rc = qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_MEMORY))) {
> @@ -8454,6 +8471,25 @@ static int qemudDomainAttachHostUsbDevice(struct qemud_driver *driver,
>          goto error;
>      }
>  
> +    if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_DEVICES)) {
> +      virCgroupPtr cgroup = NULL;
> +      usbDevice *usb;
> +
> +      if (virCgroupForDomain(driver->cgroup, vm->def->name, &cgroup, 0) !=0 ) {
> +        qemuReportError(VIR_ERR_INTERNAL_ERROR,
> +                        _("Unable to find cgroup for %s\n"),
> +                        vm->def->name);
> +        goto error;
> +      }
> +
> +      if ((usb = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
> +                               hostdev->source.subsys.u.usb.product)) == NULL)
> +        goto error;

Likewise here.

> +
> +      if (usbAllowDeviceCgroup(usb, cgroup) < 0)
> +        goto error;
> +    }

Also usbDeviceFileIterate.

> +
>      qemuDomainObjEnterMonitorWithDriver(driver, vm);
>      if (qemuCmdFlags & QEMUD_CMD_FLAG_DEVICE)
>          ret = qemuMonitorAddDevice(priv->mon, devstr);
> diff --git a/src/util/hostusb.c b/src/util/hostusb.c
> index 2d6e414..2cbe1fb 100644
> --- a/src/util/hostusb.c
> +++ b/src/util/hostusb.c
> @@ -225,3 +225,9 @@ int usbDeviceFileIterate(usbDevice *dev,
>  {
>      return (actor)(dev, dev->path, opaque);
>  }
> +
> +int usbAllowDeviceCgroup(usbDevice *dev,
> +                         virCgroupPtr group)
> +{
> +    return virCgroupAllowDevicePath(group, dev->path);
> +}

This introduces a strict coupling between the usb + cgroups
code which isn't something we want. Using the usbDeviceFileIterate
API avoids this coupling.


One general point is that the indentation in your patch is not
correct - needs to be 4 space indented rather than 2. See the
HACKING file for .emacs rules.

Regards,
Daniel
-- 
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