From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [PATCH] xencommons: Attempt to load blktap driver Date: Tue, 15 May 2012 17:21:41 +0100 Message-ID: <4FB28295.8020905@eu.citrix.com> References: <4FB29D6F0200007800083E81@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4FB29D6F0200007800083E81@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On 15/05/12 17:16, Jan Beulich wrote: >>>> On 15.05.12 at 17:49, George Dunlap wrote: >> Older kernels, such as those found in Debian Squeeze: >> * Have bugs in handling of AIO into foreign pages >> * Have blktap modules, which will cause qemu not to use AIO, but >> which are not loaded on boot. >> >> Attempt to load blktap in xencommons, to make sure modern qemu's which >> use AIO will work properly on those kernels. >> >> Signed-off-by: George Dunlap >> >> diff -r 99244350516a -r db614e92faf7 tools/hotplug/Linux/init.d/xencommons >> --- a/tools/hotplug/Linux/init.d/xencommons Tue May 15 16:48:49 2012 +0100 >> +++ b/tools/hotplug/Linux/init.d/xencommons Tue May 15 16:49:32 2012 +0100 >> @@ -59,6 +59,7 @@ do_start () { >> modprobe evtchn 2>/dev/null >> modprobe gntdev 2>/dev/null >> modprobe xen-acpi-processor 2>/dev/null >> + modprobe blktap 2>/dev/null > Can we stop manually loading all kinds of drivers here? I was > glad this went away with the switch to xencommons, and > now this is coming back. Drivers definitely needed in all cases > are acceptable imo, but backend drivers should be loaded as > backends get created by the tools (similarly frontend drivers > for the local attach case, though they should get auto-loaded > normally anyway). I tend to agree with you; I did it this way because that's what was suggested to me. But I don't at the moment know enough about the backend creation stuff in xl / qemu to DTRT here. If you want to volunteer to do a patch that DTRT, I think it makes sense to hold off. But if not, I suggest we accept this patch, and I'll come back and try to write a proper one before the 4.2 release. I think it's really important we do something before 4.2, as it causes pretty serious problems on systems which are affected (almost always a host crash, possibly with some disk corruption). -George