[Xen-devel] RE: one question to PHYSDEVOP_manage_pci_remove

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Espen Skoglund <mailto:espen.skoglund@xxxxxxxxxxxxx> wrote:
> The idea was to use PHYSDEVOP_manage_pci_{add,remove} for
> hot-pluggable devices and SR-IOV or ARI capable devices.  In general,
> when a new PCI device function is added or removed during runtime,
> dom0 will invoke the hypercall to register or unrigister the
> corresponding struct pci_dev within Xen.
> 
> Xen clears the VT-d entry because the device is about to be removed
> from the system --- either physically removed or just completely
> disabled by dom0.  The device is forcibly removed from the guest if it
> is assigned to one.  It is up to dom0 to do the actual device
> reassignment.  Although the device can not access any host memory I
> suppose it would not hurt to also do deassign_device() when the device
> is removed.  This would tear down the IOMMU page tables for the domain
> if they are not needed anymore.
> 
>       eSk

Thanks for your information, so I think at least a log is needed if the device 
is still assigned to a guest. 
Also, have you checked if dom0 have chance to "do the actual device 
reassignment"? I suppose user space tools should be involeved in such process.

Thanks
Yunhong Jiang

> 
> 
> [Yunhong Jiang]
>> Hi, Espen, when I'm working on the MSI lock issue, I have one
>> question to PHYSDEVOP_manage_pci_remove. From the kernel, seems it
>> will happen for PCI device remove. Is it target only for pci
>> hotplug?
> 
>> I asked this because I noticed that in current code, it will always
>> clear the VT-d entry, no matter if the device is owned by other
>> domain, I'm not sure if it reqiures the device is not owned by a
>> guest (maybe except dom0).
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