Description of problem: When specifying mem= or highmem= on the kernel (not HV) command-line, the kernel will crash fairly early on, in setup-xen.c. The problem seems to be that the initial setup code always assumes max_pfn >= xen_start_info->nr_pages. When specifying mem= on the kernel command-line, however, this is not the case, so the setup code actually allocates the p2m table as the sizeof max_pfn, and then attempts to copy sizeof xen_start_info->nr_pages, which overflows the table and crashes the machine. Note that this is a problem in upstream Xen, as well as in RHEL-4 PV.
Created attachment 154921 [details] Patch to fix mem= kernel parameter This is the patch I am currently testing to fix the problem when specifying mem= on the kernel command-line. Once I confirm it in my testing, I'll post it to xen-devel. Chris Lalancette
Created attachment 154933 [details] Patch to fix mem= kernel parameter (revised) Silly me; x86_64 uses end_pfn instead of max_pfn. Let's try again. Chris Lalancette
Patch posted upstream: http://lists.xensource.com/archives/html/xen-devel/2007-05/msg00804.html Chris Lalancette
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This was committed to xen-3.1-testing as c/s 15098. Chris Lalancette
This request was evaluated by Red Hat Product Management for inclusion, but this component is not scheduled to be updated in the current Red Hat Enterprise Linux release. If you would like this request to be reviewed for the next minor release, ask your support representative to set the next rhel-x.y flag to "?".
May I ask the reason for this BZ being closed WONTFIX? Was this not reproduced with 5.3rc? This event sent from IssueTracker by tumeya issue 179378
Oops. I missed that there was an IT attached to this. Basically, I hadn't seen any customer demand for it, so I thought it wasn't worth spending time on. If there is an IT attached, though, I'll open it back up. Chris Lalancette
Created attachment 335116 [details] Another version of the patch, that seems to work better for me Here's another version of the patch. This one seems to fix the crashes on both i386 and x86_64 for me. I've tested with an i386 PV guest, an x86_64 PV guest, and an x86_64 dom0; they all seem to do OK. I still need to test with an i386 dom0, but once I've done that, we should be good to go. This is essentially a backport of upstream xen-unstable c/s 15098, with two RHEL-specific tweaks. Chris Lalancette
in kernel-2.6.18-140.el5 You can download this test kernel from http://people.redhat.com/dzickus/el5 Please do NOT transition this bugzilla state to VERIFIED until our QE team has sent specific instructions indicating when to do so. However feel free to provide a comment indicating that this fix has been verified.
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An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2009-1243.html