From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [RFC PATCH 0/2] hv_netvsc: Fix shutdown regression on Win2012 hosts Date: Tue, 23 Jan 2018 08:33:36 -0800 Message-ID: <20180123083336.7e66881e@xeon-e3> References: <1516700045-32142-1-git-send-email-mgamal@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 To: Mohammed Gamal Return-path: In-Reply-To: <1516700045-32142-1-git-send-email-mgamal@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 23 Jan 2018 10:34:03 +0100 Mohammed Gamal 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(-) > The problem the original commit was trying to solve was actions in flight in the receive buffer on shutdown. Having different ordering for each version of Hyper-V seems unnecessary. There should be a way to get a stable sequence here. Let me see if I can shake more information out of the Windows team to see what the handshake on the other side is. Let's not apply this until then.