linux-kernel - Re: [PATCH v2 2/2] Revert "xen-netback: Check for hotplug-status existence before watching"

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Date:   Thu, 24 Feb 2022 09:01:17 +0000
From:   Michael Brown <mcb30@...e.org>
To:     paul@....org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>, linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Wei Liu <wei.liu@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "moderated list:XEN NETWORK BACKEND DRIVER" 
        <xen-devel@...ts.xenproject.org>,
        "open list:XEN NETWORK BACKEND DRIVER" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] Revert "xen-netback: Check for hotplug-status
 existence before watching"

On 24/02/2022 07:56, Durrant, Paul wrote:
> On 22/02/2022 00:18, Marek Marczykowski-Górecki wrote:
>> This reverts commit 2afeec08ab5c86ae21952151f726bfe184f6b23d.
>>
>> The reasoning in the commit was wrong - the code expected to setup the
>> watch even if 'hotplug-status' didn't exist. In fact, it relied on the
>> watch being fired the first time - to check if maybe 'hotplug-status' is
>> already set to 'connected'. Not registering a watch for non-existing
>> path (which is the case if hotplug script hasn't been executed yet),
>> made the backend not waiting for the hotplug script to execute. This in
>> turns, made the netfront think the interface is fully operational, while
>> in fact it was not (the vif interface on xen-netback side might not be
>> configured yet).
>>
>> This was a workaround for 'hotplug-status' erroneously being removed.
>> But since that is reverted now, the workaround is not necessary either.
>>
>> More discussion at
>> https://lore.kernel.org/xen-devel/afedd7cb-a291-e773-8b0d-4db9b291fa98@ipxe.org/T/#u 
>>
>>
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Marek Marczykowski-Górecki 
>> <marmarek@...isiblethingslab.com>
> 
> Reviewed-by: Paul Durrant <paul@....org>

In conjunction with patch 1/2 (which reverts the patch that caused the 
original problem):

Reviewed-by: Michael Brown <mbrown@...systems.co.uk>

Thanks,

Michael