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Date: Thu, 14 Mar 2019 17:10:14 +0200 From: Oleksandr Andrushchenko <andr2000@...il.com> To: Boris Ostrovsky <boris.ostrovsky@...cle.com>, netdev@...r.kernel.org, xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org, jgross@...e.com, sstabellini@...nel.org, davem@...emloft.net Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>, Volodymyr Babchuk <Volodymyr_Babchuk@...m.com> Subject: Re: [Xen-devel][PATCH] xen/netfront: Remove unneeded .resume callback On 3/14/19 5:02 PM, Boris Ostrovsky wrote: > On 3/14/19 10:52 AM, Oleksandr Andrushchenko wrote: >> On 3/14/19 4:47 PM, Boris Ostrovsky wrote: >>> On 3/14/19 9:17 AM, Oleksandr Andrushchenko wrote: >>>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com> >>>> >>>> Currently on driver resume we remove all the network queues and >>>> destroy shared Tx/Rx rings leaving the driver in its current state >>>> and never signaling the backend of this frontend's state change. >>>> This leads to the number of consequences: >>>> - when frontend withdraws granted references to the rings etc. it >>>> cannot >>>> be cleanly done as the backend still holds those (it was not told to >>>> free the resources) >>>> - it is not possible to resume driver operation as all the >>>> communication >>>> means with the backned were destroyed by the frontend, thus >>>> making the frontend appear to the guest OS as functional, but >>>> not really. >>> What do you mean? Are you saying that after resume you lose >>> connectivity? >> Exactly, if you take a look at the .resume callback as it is now >> what it does it destroys the rings etc. and never notifies the backend >> of that, e.g. it stays in, say, connected state with communication >> channels destroyed. It never goes into any other Xen bus state, so >> there is >> no way its state machine can help recovering. > > My tree is about a month old so perhaps there is some sort of regression > but this certainly works for me. After resume netfront gets > XenbusStateInitWait from backend which causes xennet_connect(). Ah, the difference can be of the way we get the guest enter the suspend state. I am making my guest to suspend with: echo mem > /sys/power/state And then I use an interrupt to the guest (this is a test code) to wake it up. Could you please share your exact use-case when the guest enters suspend and what you do to resume it? I can see no way backend may want enter XenbusStateInitWait in my use-case as it simply doesn't know we want him to. > > -boris > > Thank you, Oleksandr
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