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Date: Thu, 26 Dec 2019 15:16:44 -0800 (PST) From: David Miller <davem@...emloft.net> To: pdurrant@...zon.com Cc: xen-devel@...ts.xenproject.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, wei.liu@...nel.org, paul@....org Subject: Re: [PATCH net-next] xen-netback: support dynamic unbind/bind From: Paul Durrant <pdurrant@...zon.com> Date: Mon, 23 Dec 2019 09:59:23 +0000 > By re-attaching RX, TX, and CTL rings during connect() rather than > assuming they are freshly allocated (i.e. assuming the counters are zero), > and avoiding forcing state to Closed in netback_remove() it is possible > for vif instances to be unbound and re-bound from and to (respectively) a > running guest. > > Dynamic unbind/bind is a highly useful feature for a backend module as it > allows it to be unloaded and re-loaded (i.e. updated) without requiring > domUs to be halted. > > This has been tested by running iperf as a server in the test VM and > then running a client against it in a continuous loop, whilst also > running: > > while true; > do echo vif-$DOMID-$VIF >unbind; > echo down; > rmmod xen-netback; > echo unloaded; > modprobe xen-netback; > cd $(pwd); > brctl addif xenbr0 vif$DOMID.$VIF; > ip link set vif$DOMID.$VIF up; > echo up; > sleep 5; > done > > in dom0 from /sys/bus/xen-backend/drivers/vif to continuously unbind, > unload, re-load, re-bind and re-plumb the backend. > > Clearly a performance drop was seen but no TCP connection resets were > observed during this test and moreover a parallel SSH connection into the > guest remained perfectly usable throughout. > > Signed-off-by: Paul Durrant <pdurrant@...zon.com> Applied, thank you.
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