From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: Driver domain reboot, xenstore backend branches Date: Tue, 15 Dec 2015 17:06:18 +0000 Message-ID: <5670488A.5020808@citrix.com> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8639561443834335075==" Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Pavlo Suikov , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org --===============8639561443834335075== Content-Type: multipart/alternative; boundary="------------080101080304040805070609" --------------080101080304040805070609 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit On 15/12/15 16:38, Pavlo Suikov wrote: > Hi, > > got a question regarding reboot of a driver domain in Xen 4.5. What we > currently have is Xen 4.5, Linux in Dom0 and DomD and Android in DomU. > > On DomU start, xenstore is populated with both backend and frontend > branches for all the devices present in config. So it looks like this > (DomD is domain 1, DomU is domain 2): > > ... > /local/domain/1/backend/vif > ... > /local/domain/2/device/vif > ... > > After issuing DomD reboot, backend branches which correspond to it are > cleared, so xenstore looks like this: > > ... > /local/domain/2/device/vif > ... > > Still have frontend branch, but no corresponding backend node, since > DomU was not restarted and DomD config knows nothing about these devices. > > We want to have DomD reboot with split driver restart and backend > reconnect to hanging frontends. It there a right way to do it in Xen > 4.5 (or 4.6 for that matter if something new was introduced in this > version exactly)? > > Devd seems to be quite a tool for the job, but it observes backend > branches rather that filling them. Am I missing something here? How > split drivers are supposed to work in a DomD reboot scenario? They don't. XenServer observed the same kinds of issues when experimenting with device driver domains. We even investigated several options such as rebooting the driver domain with the same domid, and suspending/resuming the affected guests to cause them to reconnect their PV rings. Neither of these approaches worked cleanly. We came to the conclusion that rebootable driver domains is an area which will need active development work to function. ~Andrew --------------080101080304040805070609 Content-Type: text/html; charset="windows-1252" Content-Length: 2892 Content-Transfer-Encoding: quoted-printable
On 15/12/15 16:38, Pavlo Suikov wrote:
Hi,

got a question regarding reboot of a driver domain in Xen 4.5.=A0What we currently have is Xen 4.5, Linux in Dom0 and DomD and Android in DomU.

On DomU start, xenstore is populated with both backend and frontend branches for all the devices present in config. So it looks like this (DomD is domain 1, DomU is domain 2):

...
/local/domain/1/backend/vif
...
/local/domain/2/device/vif
...

After issuing DomD reboot, backend branches which correspond to it are cleared, so xenstore looks like this:

...
/local/domain/2/device/vif
...

Still have frontend branch, but no corresponding backend node, since DomU was not restarted and DomD config knows nothing about these devices.

We want to have DomD reboot with split driver restart and backend reconnect to hanging frontends. It there a right way to do it in Xen 4.5 (or 4.6 for that matter if something new was introduced in this version exactly)=3F

Devd seems to be quite a tool for the job, but it observes backend branches rather that filling them. Am I missing something here=3F How split drivers are supposed to work in a DomD reboot scenario=3F

They don't.

XenServer observed the same kinds of issues when experimenting with device driver domains.

We even investigated several options such as rebooting the driver domain with the same domid, and suspending/resuming the affected guests to cause them to reconnect their PV rings.=A0 Neither of these approaches worked cleanly.

We came to the conclusion that rebootable driver domains is an area which will need active development work to function.

~Andrew
--------------080101080304040805070609-- --===============8639561443834335075== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel --===============8639561443834335075==--