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Re: [libvirt] [PATCH 0/3] RFC: qemu: drop vioserialaddr cache



On 05/14/2016 02:25 PM, Cole Robinson wrote:
qemuDomainObjPrivate caches three lists of device addresses:

     virDomainPCIAddressSetPtr pciaddrs;
     virDomainCCWAddressSetPtr ccwaddrs;
     virDomainVirtioSerialAddrSetPtr vioserialaddrs;

Yet I can't quite tell what issue they fix... they are only used
at hotplug time for checking for address collisions, however it
appears that we can generate those lists on demand from the runtime
XML, which contains all the info we need.

In truth I only looked deeply at the vioserialaddrs list... perhaps
PCI has more to it. But at least for virtio serial it looks like
this caching can be dropped. CCing jtomko who originally added it

If this is acceptable, dropping all the caching will be a step
towards unifying all uses of qemuDomainAssignAddresses, rather
than sprinkling around a dozen call sites throughout the code.

FWIW, when I was doing stuff that touched address assignment, I noticed that priv->persistentAddrs was set to 1/0 by each of the qemuDomainAssign*Addresses() functions without regard to whether or not it had already been set by one of the other qemuDomainAssign*Addresses() functions. This meant that, for example, the VirtioSerial version could set persistentAddrs = 1, and then the PCI version could reset it back to 0. Since nobody had complained and I truthfully don't know what the usefulness of the cache is, I didn't touch it. It does look like any domain that has no PCI addresses ends up with persistentAddrs == 0, so probably the cache is empty anyway (? I guess. I didn't actually look at what's behind that faux-boolean).


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