RE: [PATCH 0/2] Drivers: hv: vmbus: make bus ids in sysfs persistent

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> Sent: Monday, August 15, 2016 9:11 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: devel@xxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>
> Subject: Re: [PATCH 0/2] Drivers: hv: vmbus: make bus ids in sysfs persistent
> 
> KY Srinivasan <kys@xxxxxxxxxxxxx> writes:
> 
> >> -----Original Message-----
> >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> >> Sent: Thursday, August 11, 2016 2:17 AM
> >> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> >> Cc: devel@xxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Haiyang
> Zhang
> >> <haiyangz@xxxxxxxxxxxxx>
> >> Subject: Re: [PATCH 0/2] Drivers: hv: vmbus: make bus ids in sysfs persistent
> >>
> >> KY Srinivasan <kys@xxxxxxxxxxxxx> writes:
> >>
> >> >> -----Original Message-----
> >> >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx]
> >> >> Sent: Tuesday, August 9, 2016 1:46 AM
> >> >> To: devel@xxxxxxxxxxxxxxxxxxxxxx
> >> >> Cc: linux-kernel@xxxxxxxxxxxxxxx; Haiyang Zhang
> >> >> <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>
> >> >> Subject: [PATCH 0/2] Drivers: hv: vmbus: make bus ids in sysfs
> >> >> persistent
> >> >>
> >> >> Bus ids for VMBus devices in /sys/bus/vmbus/devices/ are not
> >> >> guaranteed to be persistent across reboot or kernel restart and this
> >> >> causes problems for some tools. E.g. kexec tools use these ids to identify
> >> NIC on kdump.
> >> >> Fix the issue by using relid from channel offer as the unique id
> >> >> instead of an auto incremented counter.
> >> >
> >> > Relids are not persistent. It is only valid between a channel offer
> >> > message and a relid released message (or an unload or initiate contact
> >> > message, which invalidates all channels). This is an opaque number
> >> > that the root generates and uses to track channels. There is no
> >> > guarantee that the same type of channel (networking, storage, etc)
> >> > will get the same relid on each reboot.
> >> >
> >>
> >> Thanks for the info,
> >>
> >> can we use device_id (offermsg.offer.if_instance.b) instead?
> >
> > I think you could; I am going to verify and get back to you on this.
> 
> Thanks!

The instance GUID is guaranteed to be persistent between boots and also across live migration.

K. Y