Re: [libvirt] [PATCH] qemu: auto-create pci controller alias if missing from domain status
On 01/07/2014 05:20 PM, Eric Blake wrote:
On 01/07/2014 07:53 AM, Laine Stump wrote:
> I'm not 100% convinced that it's necessary to handle *this* case
> either (upgrading from pre-1.0.2), but thought I should send the patch
> to the list anyway to see what others think. My opinion is that it's
> creating permanent clutter in the code in order to handle a situation
> that will come up just once in the entire lifetime of a host (and even
> then only if libvirt is upgraded without somehow restarting a guest,
> and *then* a device is hotplugged to that guest), so it may be better
> if we just left the workaround ("restart/save-restore/migrate the
> domain if you need to hotplug a device") as a footnote somewhere
> instead.
Yes, I think I could live with such a footnote. And even if we get
outvoted and someone else requests the permanent code clutter, we can
add that as a separate commit which gives the further justification of
why we are adding it.
Okay. I *think* that the bugzilla record and this email thread should be
enough that anyone encountering the problem will find the solution after
a quick google search. I don't know that putting it in libvirt release
notes would be of any use, since the release it *should* have been noted
in is long past...
> + /* this could be a case where the domain had
been
> + * started with an earlier version of libvirt that
> + * had no device entry for the PCI bus
> + * (pre-1.0.2), and in that case no alias would be
> + * set in the status XML, so we create one using
> + * the standard "pci.N" pattern.
> + */
> + if (virAsprintf(&tempAlias, "pci.%u",
info->addr.pci.bus) < 0)
> + goto cleanup;
> + contAlias = tempAlias;
contAlias and tempAlias point to the same location...
It's a bit of a moot point since we're not going to push it, but...
contAlias is just a const char * that normally would be a duplicate of
cont->info.alias. Since cont->info.alias is NULL, I create a temporary
alias in tempAlias and duplicate that instead.
> }
> break;
> }
> @@ -3118,6 +3123,7 @@ qemuBuildDeviceAddressStr(virBufferPtr buf,
> ret = 0;
> cleanup:
> VIR_FREE(devStr);
> + VIR_FREE(tempAlias);
and you then free tempAlias. That leaves contAlias pointing at stale
memory. That doesn't feel right.
But by this time contAlias is already long ago out of scope.