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Date:   Fri, 26 Jan 2018 10:10:42 -0800
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     Mohammed Gamal <mgamal@redhat.com>
Cc:     netdev@vger.kernel.org, otubo@redhat.com, sthemmin@microsoft.com,
        haiyangz@microsoft.com, linux-kernel@vger.kernel.org,
        devel@linuxdriverproject.org, vkuznets@redhat.com
Subject: Re: [RFC PATCH 0/2] hv_netvsc: Fix shutdown regression on Win2012
 hosts
Message-ID: <20180126101042.0300d836@xeon-e3>
In-Reply-To: <1516700045-32142-1-git-send-email-mgamal@redhat.com>
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On Tue, 23 Jan 2018 10:34:03 +0100
Mohammed Gamal <mgamal@redhat.com> wrote:

> Commit 0cf737808ae7 ("hv_netvsc: netvsc_teardown_gpadl() split") introduced
> a regression that caused VMs not to shutdown after netvsc_device_remove() is
> called. This is caused by GPADL teardown sequence change, and while that was 
> necessary to fix issues with Win2016 hosts, it did introduce a regression for
> earlier versions.
> 
> Prior to commit 0cf737808 the call sequence in netvsc_device_remove() was as 
> follows (as implemented in netvsc_destroy_buf()):
> 1- Send NVSP_MSG1_TYPE_REVOKE_RECV_BUF message
> 2- Teardown receive buffer GPADL
> 3- Send NVSP_MSG1_TYPE_REVOKE_SEND_BUF message
> 4- Teardown send buffer GPADL
> 5- Close vmbus
> 
> This didn't work for WS2016 hosts. Commit 0cf737808 split netvsc_destroy_buf()
> into two functions and rearranged the order as follows
> 1- Send NVSP_MSG1_TYPE_REVOKE_RECV_BUF message
> 2- Send NVSP_MSG1_TYPE_REVOKE_SEND_BUF message
> 3- Close vmbus
> 4- Teardown receive buffer GPADL
> 5- Teardown send buffer GPADL
> 
> That worked well for WS2016 hosts, but for WS2012 hosts it prevented VMs from
> shutting down. 
> 
> This patch series works around this problem. The first patch splits
> netvsc_revoke_buf() and netvsc_teardown_gpadl() into two finer grained
> functions for tearing down send and receive buffers individally. The second patch
> uses the finer grained functions to implement the teardown sequence according to
> the host's version. We keep the behavior introduced in 0cf737808ae7 for Windows
> 2016 hosts, while we re-introduce the old sequence for earlier verions.
> 
> Mohammed Gamal (2):
>   hv_netvsc: Split netvsc_revoke_buf() and netvsc_teardown_gpadl()
>   hv_netvsc: Change GPADL teardown order according to Hyper-V version
> 
>  drivers/net/hyperv/netvsc.c | 50 +++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 42 insertions(+), 8 deletions(-)
> 

What I am experimenting with is sending an NDIS_RESET (instead of setting packet filter)
as part of the close processing. This seems more like what the description of what Windows
driver does and matches my reading of the public RNDIS specification.