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Re: [libvirt] [PATCH v3] qemu: Honor the orginal PCI dev properties when reattaching



于 2011年10月15日 05:47, Eric Blake 写道:
On 10/13/2011 02:30 AM, Osier Yang wrote:
BZ# https://bugzilla.redhat.com/show_bug.cgi?id=736214

The problem is caused by the original info of domain's PCI dev is
maintained by qemu_driver->activePciHostdevs list, (E.g. dev->reprobe,
which stands for whether need to reprobe driver for the dev when do
reattachment). The fields (dev->reprobe, dev->unbind_from_stub, and
dev->remove_slot) are initialized properly when preparing the PCI
device for managed attachment. However, when do reattachment, it
construct a complete new "pciDevice" without honoring the original
dev info, and thus the dev won't get the original driver or can get
other problem.

This patch is to fix the problem by get the devs from list
driver->activePciHostdevs.

Tested with following 3 scenarios:
   * the PCI was bound to some driver not pci-stub before attaching

     result: the device will be bound to the original driver

   * the PCI was bound to pci-stub before attaching

     result: no driver reprobing, and still bound to pci-stub

   * The PCI was not bound to any driver

     result: no driver reproing, and still not bound to any driver.

s/reproing/reprobing/


I like v3 better, even though it has the longer diffstat, because it divides the work into smaller self-contained functions rather than making an already long function longer.

However, I got a merge conflict when applying on top of your other pci hostdev fixup patch; but I think I resolved that correctly.

ACK and pushed, after I reproduced the issue and tested that the patch fixes it.

Thanks.


It didn't help matters that virt-manager has a bug. It manually calls the equivalent of 'nodedev-detach' prior to hot-plugging any hostdev device, _even though it requests managed=1_. That means the device is already bound to pci-stub before the hotplug attempt is started; and on failure to hotplug, libvirt _faithfully_ restores the the device back to its original state (still pci-stub), but virt-manager does not recognize the error condition and does not call nodedev-reattach.

Probally we need to improve the documents for "managed" host device, user
completely doesn't known what will happen if the device was bound to driver
not pci-stub or not bound to any driver from the existed documents.

" When <code>managed</code> is "yes" for a PCI device, it is detached from
the host before being passed on to the guest."

I could imaging one day some way will file bug for it.

And also "managed" is used for USB device too, however, we don't do
any reattachment for USB device actually. Do we need documents to
tell the truth? though we might add the support soon.

Osier


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