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Re: [libvirt] [PATCH 0/8] Hostdev-hybrid patches

On 09/13/2012 06:16 AM, Shradha Shah wrote:
> On 09/11/2012 08:07 PM, Laine Stump wrote:
>> If so, one issue I have is that one of the devices (the
>> pci-passthrough?) doesn't have its guest-side PCI address visible
>> anywhere in the guest's XML, does it? This is problematic, because
>> management applications (and libvirt itself) expect to be able to scan
>> the list of devices to learn what PCI slots are occupied on the guest,
>> and where they can add new devices.
> Actually the guest PCI address of the pci-passthrough device i.e. The VF
> is visible in the guest's XML when the guest is running. The VF will be plugged
> into the guest only when the guest is running or when the guest is not being 
> migrated hence will be visible in the guest XML.

But there's only a place for one guest-side PCI address in each device
element. Where is it showing up?

Also, we really need for the same PCI address to be used each time the
device is attached; although there may not appear to be a need for that
now, past experience has shown that changing the PCI slot of a device
over time inevitably leads to a problem somewhere with something :-/

Due to this, the general complexity of what's being done vs. what's
being added, and also time/review bandwidth constraints I think that at
least for this release we can't take the full hostdev-hybrid device
patchset (really I think it will need to be re-thought and probably a
different approach taken for specifying the two devices).

However, the "ephemeral" attribute for <hostdev>, <interface
type='hostdev'> and <forward mode='hostdev'> is fairly straightforward
and provides generally useful new functionality (especially if it is
expanded as mentioned to work for save/restore as well as migration) -
with just this part of your patch, we can still get all of the desired
functionality at the level of libvirt XML (with the two limitations of
1) networks limited to a single PF, and 2) duplicated mac addresses must
be manually specified).

How difficult would it be to create a patch with just that part of the
functionality (plus the additional save/restore tweak)? If you could do
that before the freeze on Tuesday AM we might be able to get it into
0.10.2 (which will be what Fedora 18 is based on).

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