[Xen-devel] [PATCH] x86/amd: Fix xen_apic_write warnings in Dom0

[Wei Wang <wei.wang2@xxxxxxx>]

Hi, this patch fixes a 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>

Thanks
Wei

Attachment: 0001-Fix-xen_apic_write-warnings-in-Dom0.patch
Description: 0001-Fix-xen_apic_write-warnings-in-Dom0.patch

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel