Michael Walle
2013-Jan-21 18:36 UTC
[Pkg-xen-devel] Bug#698651: xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be unexpectedly enabled on Dom0
Package: xen-hypervisor-4.1-amd64 Version: 4.1.3-7 Severity: important Tags: patch Dear Maintainer, The PMU may be enabled on the Dom0 although the needed MSRs are not accessible, causing at least major noise on the xen messages ring buffer. I suspect there might also be a performance decrease, because the MSR write is trapped by Xen. Once the PC is in that state, a reboot won't help. This bug is fixed in Xen upstream: http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=cabea9d59f1783167a79fa7a550ced04b3506f3c I've successfully tested this patch on the debian kernel from wheezy. How to reproduce: - boot bare metal kernel (that is, no xen hypervisor) - (re)boot dom0 with xen This results in the following kernel warning: [ 0.016036] ------------[ cut here ]------------ [ 0.016070] WARNING: at /build/buildd-linux_3.2.35-2-amd64-v9djlH/linux-3.2.35/arch/x86/xen/enlighten.c:738 init_hw_perf_events+0x246/0x3e1() [ 0.016107] Hardware name: MS-7368 [ 0.016135] Modules linked in: [ 0.016189] Pid: 1, comm: swapper/0 Not tainted 3.2.0-4-amd64 #1 Debian 3.2.35-2 [ 0.016224] Call Trace: [ 0.016257] [<ffffffff81046a75>] ? warn_slowpath_common+0x78/0x8c [ 0.016289] [<ffffffff816b2f72>] ? init_hw_perf_events+0x246/0x3e1 [ 0.016319] [<ffffffff816b2d2c>] ? check_bugs+0x2b/0x2b [ 0.016351] [<ffffffff81002085>] ? do_one_initcall+0x75/0x12c [ 0.016383] [<ffffffff816abbcb>] ? kernel_init+0x8d/0x152 [ 0.016414] [<ffffffff81354174>] ? kernel_thread_helper+0x4/0x10 [ 0.016447] [<ffffffff81352233>] ? int_ret_from_sys_call+0x7/0x1b [ 0.016479] [<ffffffff8134d37c>] ? retint_restore_args+0x5/0x6 [ 0.016509] [<ffffffff81354170>] ? gs_change+0x13/0x13 [ 0.016545] ---[ end trace 4fbe30a09b2591f0 ]--- [ 0.016576] ... version: 0 [ 0.016605] ... bit width: 48 [ 0.016633] ... generic registers: 4 [ 0.016662] ... value mask: 0000ffffffffffff [ 0.016691] ... max period: 00007fffffffffff [ 0.016721] ... fixed-purpose events: 0 [ 0.016749] ... event mask: 000000000000000f [ 0.016971] NMI watchdog enabled, takes one hw-pmu counter. [ 0.017012] ------------[ cut here ]------------ and the following (repeating) output on the xen messages ring buffer: (XEN) printk: 28 messages suppressed. (XEN) traps.c:2488:d0 Domain attempted WRMSR 00000000c0010000 from 0x0000000000130076 to 0x0000000000530076. (XEN) printk: 52 messages suppressed. (XEN) traps.c:2488:d0 Domain attempted WRMSR 00000000c0010000 from 0x0000000000130076 to 0x0000000000530076. (XEN) printk: 27 messages suppressed. [..] -- System Information: Debian Release: 7.0 APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores) Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash xen-hypervisor-4.1-amd64 depends on no packages. Versions of packages xen-hypervisor-4.1-amd64 recommends: ii xen-utils-4.1 4.1.3-7 Versions of packages xen-hypervisor-4.1-amd64 suggests: ii xen-docs-4.1 4.1.3-7 -- no debconf information
Debian Bug Tracking System
2013-Jan-31 15:06 UTC
[Pkg-xen-devel] Bug#698651: marked as done (xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be unexpectedly enabled on Dom0)
Your message dated Thu, 31 Jan 2013 15:03:48 +0000 with message-id <E1U0vg4-0004AW-B8 at franck.debian.org> and subject line Bug#698651: fixed in xen 4.1.4-1 has caused the Debian Bug report #698651, regarding xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be unexpectedly enabled on Dom0 to be marked as done. This means that you claim that the problem has been dealt with. If this is not the case it is now your responsibility to reopen the Bug report if necessary, and/or fix the problem forthwith. (NB: If you are a system administrator and have no idea what this message is talking about, this may indicate a serious mail system misconfiguration somewhere. Please contact owner at bugs.debian.org immediately.) -- 698651: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=698651 Debian Bug Tracking System Contact owner at bugs.debian.org with problems -------------- next part -------------- An embedded message was scrubbed... From: Michael Walle <michael at walle.cc> Subject: xen-hypervisor-4.1-amd64: PMU (performance monitoring) unit may be unexpectedly enabled on Dom0 Date: Mon, 21 Jan 2013 19:36:52 +0100 Size: 4653 URL: <http://lists.alioth.debian.org/pipermail/pkg-xen-devel/attachments/20130131/12d18d2e/attachment.mht> -------------- next part -------------- An embedded message was scrubbed... From: Bastian Blank <waldi at debian.org> Subject: Bug#698651: fixed in xen 4.1.4-1 Date: Thu, 31 Jan 2013 15:03:48 +0000 Size: 8677 URL: <http://lists.alioth.debian.org/pipermail/pkg-xen-devel/attachments/20130131/12d18d2e/attachment-0001.mht>
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