[Xen-devel] [PATCH 0/5] xend: Notify xend of udev hardware events

[Yosuke Iwamatsu <y-iwamatsu@xxxxxxxxxxxxx>]

Zhigang Wang wrote:
> Yosuke Iwamatsu wrote:
>> There are several xen-api classes that represent physical devices,
>> such as PIF, PPCI and PSCSI. At the initialization step, xend creates
>> instances of these classes and stores them, so as to later expose
>> the host's available physical resources to remote clients.
>>
>> The problem is that, when you hot-add of hot-remove a physical device
>> to of from the host, currently there is no way xend can detect that.
>> So the physical resource information kept in xend may become inconsistent
>> with the real state. 
>>
>> This series of patches makes xend get notification of hardware changes
>> and update the physical resource information. Inside xend, we runs a thread
>> which opens a socket and listens to events of hardware configuration changes
>> from udev mechanism.
>>
> we already have XendMonitor to do that. Is it right to add these patches?

XendMonitor is only used to fetch the usage statistics of some devices from
from procfs and is not suitable to monitor the configuration changes of
physical devices, I think. We may be able to implement in XendMonitor a
detection mechanism of physical device's hot-plugging by polling sysfs entries,
but that would take some amount of effort and I don't see any advantage to do it
instead of utilizing udev mechanism.

Thanks,
  -- Yosuke

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