Re: [Xen-devel] [PATCH] Test tap devices in testDeviceComplete()

[Jiri Denemark <jdenemar@xxxxxxxxxx>]

> > XendDomainInfo.testDeviceComplete() should check block devices have
> > shutdown correctly but it only considers vbd class devices and ignores tap
> > devices. The attached patch changes testDeviceComplete() to wait for both
> > vbd and tap devices to be shutdown correctly.
> 
> Has this also been tested with PV guests ?  In that case, there are no tap 
> devices to shutdown.

Hmm, testDeviceComplete() is called after _releaseDevices(), which destroys
all devices. And even for a PV guest, I can see tap devices in
/vm/UUID/device/tap tree in xenstore.

vm = ""
 0829a755-d2ed-607e-5847-ce9ec19e7422 = ""
  image = "(linux (kernel ) (videoram 4) (notes..."
   ostype = "linux"
   kernel = "/var/run/xend/boot/boot_kernel.QsXCO7"
   cmdline = "ro root=LABEL=/ selinux=0"
   ramdisk = "/var/run/xend/boot/boot_ramdisk.UzyMl2"
  device = ""
   tap = ""
    51712 = ""
     frontend = "/local/domain/2/device/vbd/51712"
     frontend-id = "2"
     backend-id = "0"
     backend = "/local/domain/0/backend/tap/2/51712"

That is, that device will be destroyed by _releaseDevices although not tested
by testDeviceComplete to be completed.

Anyway, this is a bit hard to test, as this code patch is only used when
guest's kernel lacks SUSPEND_CANCEL feature, which is present in current Xen
kernels. While, I have a kernel without this feature, it also lacks some other
parts and the guest crashes...

On the other hand, I tested this on older Xen tools which match the kernel.
This code path hasn't really changed since than.

Jirka

-- 
Immorality: the morality of those who are having a better time.
                -- H. L. Mencken

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