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

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Date:	Wed, 10 Aug 2016 19:00:37 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Haiyang Zhang" <haiyangz@...rosoft.com>
Subject: RE: [PATCH 0/2] Drivers: hv: vmbus: make bus ids in sysfs persistent



> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Tuesday, August 9, 2016 1:46 AM
> To: devel@...uxdriverproject.org
> Cc: linux-kernel@...r.kernel.org; Haiyang Zhang <haiyangz@...rosoft.com>;
> KY Srinivasan <kys@...rosoft.com>
> 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.

Regards,

K. Y
> 
> Vitaly Kuznetsov (2):
>   Drivers: hv: make VMBus bus ids persistent
>   Drivers: hv: get rid of id in struct vmbus_channel
> 
>  drivers/hv/channel_mgmt.c | 2 --
>  drivers/hv/vmbus_drv.c    | 2 +-
>  include/linux/hyperv.h    | 3 ---
>  3 files changed, 1 insertion(+), 6 deletions(-)
> 
> --
> 2.7.4