On Thu, 2010-02-25 at 10:18 +0100, Bastian Blank wrote: > On Thu, Feb 25, 2010 at 07:33:26AM +0000, Ian Campbell wrote: > > Is it acceptable to backport > > http://git.kernel.org/?p=linux/kernel/git/tip/linux-2.6-tip.git;a=commitdiff;h=a73a040e3b18521f83e726abacc2f3992a148388 > > into the sid kernel? > > Will it show up in Linus tree any time soon?
Hopefully in the 2.6.33 merge window but I will check with x86 maintainers. > > The followup Xen patch is > > http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=commitdiff;h=9be6abceadd654543648b799ae430f30e09959ac > > and disables HIGHPTE when running under Xen. It prevents crashes under > > load due to HIGHPTE races which cannot be otherwise (easily) avoided > > under Xen. > > The commit message does not describe why, and it is not obvious to me. It's a race between pinning a page and kmap/kunmap. There's a path in the pagefault code where the kernel breaks its own locking rules by kmapping a high pte page without holding the pagetable lock which breaks Xen's ability to track the pinned/unpinned state of the page. (I'm going to ask Jeremy to update the commit to include this paragraph of explanation). Jeremy gave some explanation in: http://lists.xensource.com/archives/html/xen-devel/2010-01/msg00921.html (which I've blatantly stolen above) The thread which led to the patch is "[Xen-devel] dom0 pvops crash" and "[Xen-devel] Xen pvops kernel CONFIG_HIGHPTE race/crash" involving Pasi Kärkkäinen. It's quite long but the final conclusion starts at: http://lists.xensource.com/archives/html/xen-devel/2010-02/msg00403.html That thread starts at: http://lists.xensource.com/archives/html/xen-devel/2010-01/msg00902.html and there is an older version of the same issue at: http://lists.xensource.com/archives/html/xen-devel/2009-06/msg00519.html > I'm not sure, but I think this should be possible to do via stable after > both patches landed where they belong. OK will go that route assuming I get confirmation that the patch is destined for 2.3.32. If not then would a backport be appropriate? Ian. -- Ian Campbell Current Noise: Autopsy - Pagan Saviour (Live '90) Q: Why haven't you graduated yet? A: Well, Dad, I could have finished years ago, but I wanted my dissertation to rhyme. -- To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/1267109053.11737.10729.ca...@zakaz.uk.xensource.com