[Xen-changelog] [xen-unstable] x86/amd: Fix xen_apic_write warnings in Dom0

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Wei Wang <wei.wang2@xxxxxxx>
# Date 1350306216 -7200
# Node ID 983108e1b56bf809f3f5eaaebf18c4b613ff0865
# Parent  137dfbd3190e849b3a498d8b2ea282ebbf12e77d
x86/amd: Fix xen_apic_write warnings in Dom0

[    0.020294] ------------[ cut here ]------------
[    0.020311] WARNING: at arch/x86/xen/enlighten.c:730
xen_apic_write+0x15/0x17()
[    0.020318] Hardware name: empty
[    0.020323] Modules linked in:
[    0.020334] Pid: 1, comm: swapper/0 Not tainted 3.3.8 #7
[    0.020340] Call Trace:
[    0.020354]  [<ffffffff81050379>] warn_slowpath_common+0x80/0x98
[    0.020369]  [<ffffffff810503a6>] warn_slowpath_null+0x15/0x17
[    0.020378]  [<ffffffff810034df>] xen_apic_write+0x15/0x17
[    0.020392]  [<ffffffff8101cb2b>] perf_events_lapic_init+0x2e/0x30
[    0.020410]  [<ffffffff81ee4dd0>] init_hw_perf_events+0x250/0x407
[    0.020419]  [<ffffffff81ee4b80>] ? check_bugs+0x2d/0x2d
[    0.020430]  [<ffffffff81002181>] do_one_initcall+0x7a/0x131
[    0.020444]  [<ffffffff81edbbf9>] kernel_init+0x91/0x15d
[    0.020456]  [<ffffffff817caaa4>] kernel_thread_helper+0x4/0x10
[    0.020471]  [<ffffffff817c347c>] ? retint_restore_args+0x5/0x6
[    0.020481]  [<ffffffff817caaa0>] ? gs_change+0x13/0x13
[    0.020500] ---[ end trace a7919e7f17c0a725 ]---

Kernel function check_hw_exists() writes 0xabcd to msr 0xc0010201 (Performance 
Event
Counter 0) and read it again to check if it is running as dom0. Early amd cpus 
does
not reset perf counters during warm reboot. If the kernel is booted with bare 
metal
and then as a dom0, the content of msr 0xc0010201 will stay and the checking 
will
pass and PMU will be enabled unexpectedly.

Signed-off-by: Wei Wang <wei.wang2@xxxxxxx>

Don't reset the counters when used for the NMI watchdog.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
Committed-by: Jan Beulich <jbeulich@xxxxxxxx>
---


diff -r 137dfbd3190e -r 983108e1b56b xen/arch/x86/cpu/amd.c
--- a/xen/arch/x86/cpu/amd.c    Mon Oct 15 12:59:14 2012 +0200
+++ b/xen/arch/x86/cpu/amd.c    Mon Oct 15 15:03:36 2012 +0200
@@ -11,6 +11,7 @@
 #include <asm/hvm/support.h>
 #include <asm/setup.h> /* amd_init_cpu */
 #include <asm/acpi.h>
+#include <asm/apic.h>
 
 #include "cpu.h"
 
@@ -485,6 +486,17 @@ static void __devinit init_amd(struct cp
        if (c->x86 > 0x11)
                set_bit(X86_FEATURE_ARAT, c->x86_capability);
 
+       /*
+        * Prior to Family 0x14, perf counters are not reset during warm reboot.
+        * We have to reset them manually.
+        */
+       if (nmi_watchdog != NMI_LOCAL_APIC && c->x86 < 0x14) {
+               wrmsrl(MSR_K7_PERFCTR0, 0);
+               wrmsrl(MSR_K7_PERFCTR1, 0);
+               wrmsrl(MSR_K7_PERFCTR2, 0);
+               wrmsrl(MSR_K7_PERFCTR3, 0);
+       }
+
        if (cpuid_edx(0x80000007) & (1 << 10)) {
                rdmsr(MSR_K7_HWCR, l, h);
                l |= (1 << 27); /* Enable read-only APERF/MPERF bit */

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