From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Lalancette Subject: Re: [PATCH] Fix xenconsole after aborted save Date: Wed, 22 Apr 2009 16:24:20 +0200 Message-ID: <49EF2894.4090208@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Keir Fraser Cc: Jiri Denemark , "xen-devel@lists.xensource.com" , Gerd Hoffmann List-Id: xen-devel@lists.xenproject.org Keir Fraser wrote: > On 22/04/2009 10:49, "Chris Lalancette" wrote: > >> Keir Fraser wrote: >>> Another thing to note is I think this problem can only occur if the domU >>> does not support suspend cancellation (advertised as SUSPEND_CANCEL in >>> kernel elf notes -- see xen/xend/XendDomainInfo.py:resumeDomain()). Your >>> kernels should support that feature -- suspend cancellation (a.k.a. Resume) >>> is very likely to be hit-or-miss without it! >> Could you elaborate a bit on this? I was under the impression that suspend >> cancellation was there mostly for the netaccel bits, but I have to admit I >> didn't look at it very closely. What scenarios do the suspend cancel bits >> help? > > Suspend failures (failure to save or to migrate). Also for live > checkpointing/snapshotting. The feature indicates that the guest is happy > for the suspend hypercall to return indicating 'failure/cancelled' and in > which case it can pretty much resume whatever it was doing without any of > the usual resume logic. The alternative is for the toolstack to make it look > like the domain has been restored/migrated, by resetting PV devices and the > like, and this is not much tested and almost inherently fragile. > > The suspend_cancel hook you are thinking of is for any PV devices which *do* > need to know that a suspend was cancelled. Netaccel does for some reason > which I cannot recall. > > Anyway, it is pretty easy and pretty important to support SUSPEND_CANCEL! OK, that makes sense. Thanks Keir! -- Chris Lalancette