[Xen-devel] Re: [patch] Fix xm pci-detach for inactive devices

[Simon Horman <horms@xxxxxxxxxxxx>]

On Tue, May 26, 2009 at 01:15:51PM +0800, Zhai, Edwin wrote:
> Simon,
> What does inactive domain means?
> How does it lead an invalid vslot?

Hi Edwin,

An inactive domain means one that has been created
but is stopped. An invalid vslot can occur in this case
if the vslot is to be automatically assigned by qemu-dm.
This is because the request will not be sent to qemu-dm
until the domain is started.

e.g.:

$ xm new hvm.conf
$ xm pci-attach hvm 00:1d.0
$ xm pci-list hvm
-    0x0      0x00  0x1d   0x0   <- '-' means the vslot has not been determined
$ xm pci-detach hvm 00:1d.0      <- will fail without this change

Or alternatively:

$ xm new hvm.conf
$ xm pci-attach hvm 00:1d.0
$ xm pci-list hvm
-    0x0      0x00  0x1d   0x0   <- '-' means the vslot has not been determined
$ xm start hvm
$ xm pci-list hvm
0x7  0x0      0x00  0x1d   0x0   <- vslot 0x7 was allocated after the
                                    domain started
$ xm pci-detach hvm 00:1d.0      <- will work with or without this patch

Attaching devices to inactive domains was recently
fixed (added?) by Kanno-san.

> Simon Horman wrote:
>> In the case where a device is attached to an inactive domain
>> and then removed before the domain is activated it won't have
>> a vslot assigned, but it should still be valid to remove it.
>>
>> I don't think that there are any other cases where vslot can
>> be invalid.
>>
>> Lightly tested
>>
>> Cc: Zhai Edwin <edwin.zhai@xxxxxxxxx>
>> Cc: Masaki Kanno <kanno.masaki@xxxxxxxxxxxxxx>
>> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
>>
>> Index: xen-unstable.hg/tools/python/xen/xend/XendDomainInfo.py
>> ===================================================================
>> --- xen-unstable.hg.orig/tools/python/xen/xend/XendDomainInfo.py     
>> 2009-05-26 14:37:15.000000000 +1000
>> +++ xen-unstable.hg/tools/python/xen/xend/XendDomainInfo.py  2009-05-26 
>> 14:37:18.000000000 +1000
>> @@ -1130,9 +1130,6 @@ class XendDomainInfo:
>>          if devnum >= pci_len:
>>              raise VmError("Device @ vslot 0x%x doesn't exist." % (vslot))
>>  -        if vslot == AUTO_PHP_SLOT:
>> -            raise VmError("Device @ vslot 0x%x doesn't support hotplug." % 
>> (vslot))
>> -
>>          # Check the co-assignment.
>>          # To pci-detach a device D from domN, we should ensure: for each DD 
>> in the
>>          # list of D's co-assignment devices, DD is not assigned (to domN).
>>
>>   
>
> -- 
> best rgds,
> edwin

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