RE: [RFC PATCH 0/2] hv_netvsc: Fix shutdown regression on Win2012 hosts

[Haiyang Zhang]

> -----Original Message-----
> From: Mohammed Gamal [mailto:mgamal@xxxxxxxxxx]
> Sent: Tuesday, January 23, 2018 4:34 AM
> To: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; KY
> Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>;
> Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>; vkuznets@xxxxxxxxxx;
> cavery@xxxxxxxxxx; otubo@xxxxxxxxxx; Mohammed Gamal
> <mgamal@xxxxxxxxxx>
> Subject: [RFC PATCH 0/2] hv_netvsc: Fix shutdown regression on Win2012
> hosts
> 
> 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(-)

Thank you for the patches. We are testing them internally.

- Haiyang