From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] Revert "xen-hvm: increase maxmem before calling xc_domain_populate_physmap" Date: Tue, 16 Jun 2015 18:01:23 +0100 Message-ID: <1434474083.3342.114.camel@citrix.com> References: <1433940913-19425-1-git-send-email-george.dunlap@eu.citrix.com> <20150616113305.GA30895@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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: Stefano Stabellini Cc: George Dunlap , Stefano Stabellini , Andrew Cooper , Wei Liu , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Tue, 2015-06-16 at 16:51 +0100, Stefano Stabellini wrote: > > I think reverting this change in QEMU and relevant changes in libxl > > would be the most viable solution to solve this for this release. > > Reverting this patch doesn't really solve the problem: instead of > breaking on migration when the VM has more than 3 emulated NICs, the VM > simply refuses to start in that case. I guess it can be considered a > small improvement but certainly not a fix. > > Given that the migration issue only happens in an "unusual corner case", > are we really in a hurry to revert this commit and go back to the > failure to start, even before we actually figure out what the proper fix > is? I don't care about migration (particularly). I care about the brokeness in libxl which has been introduced while trying to cope with this QEMU change. We should revert now so that we can revert those libxl changes too and get ourselves to a known state which doesn't have races in the memory setting code. It will also be much easier to move forward from a state where QEMU is not messing with the memory limit for a domain in an uncoordinated way and only libxl is doing so. Every QEMU release which we delay this revert will just make it harder to find a path safe forward towards whatever design we finally settle on. Ian.