From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [kvm-devel] guest crash on 2.6.20-rc4 Date: Tue, 09 Jan 2007 23:26:48 +0200 Message-ID: <45A40898.4040307@qumranet.com> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------020502030200070109080303" Cc: kvm-devel , linux-kernel@vger.kernel.org Return-path: To: Roland Dreier In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org This is a multi-part message in MIME format. --------------020502030200070109080303 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Roland Dreier wrote: > I'm running a 64-bit Fedora 6 install as a guest on a host running > 2.6.20-rc4 with the kvm-10 userspace release. The CPU is a Xeon 5160 > and I have 6 GB of RAM. The guest is given 512 MB of memory. I left > the guest idle overnight, and the makewhatis cron job seems to have > triggered this: > > Unable to handle kernel paging request at ffff81000ba04000 RIP: > [] clear_page+0x16/0x44 > I've managed to reproduce a bug with similar characteristics: a write fault into a present, writable kernel page. The attached patch should fix it. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. --------------020502030200070109080303 Content-Type: text/x-patch; name="spurious-page-fault.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="spurious-page-fault.patch" Index: b/drivers/kvm/paging_tmpl.h =================================================================== --- a/drivers/kvm/paging_tmpl.h (revision 4270) +++ b/drivers/kvm/paging_tmpl.h (working copy) @@ -274,7 +274,7 @@ struct kvm_mmu_page *page; if (is_writeble_pte(*shadow_ent)) - return 0; + return 1; writable_shadow = *shadow_ent & PT_SHADOW_WRITABLE_MASK; if (user) { --------------020502030200070109080303--