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RE: [Xen-devel] [PATCH] Append 'nohpet' in dom0 cmdline to prevent dom0 from using HPET

  • To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
  • From: "Wei, Gang" <gang.wei@xxxxxxxxx>
  • Date: Thu, 15 Oct 2009 11:31:39 +0800
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Delivery-date: Wed, 14 Oct 2009 20:32:19 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcpNCKaBrvPTCpZlRnyPo/xyul0pxgAKWEngAAVj+NA=
  • Thread-topic: [Xen-devel] [PATCH] Append 'nohpet' in dom0 cmdline to prevent dom0 from using HPET

>>> Append 'nohpet' in dom0 cmdline to prevent dom0 from using HPET
>>> Xen is using HPET to wakeup cpu from deep c-states, so the HPET
>>> usage in dom0 must be fobidden. In 2.6.18-xen, the HPET was by
>>> default disabled in config file. For upstream kernel built for pv
>>> dom0, it is not practical to disable dom0 HPET usage in that way
>>> because the same image may be also using as bare metal kernerl. So
>>> add cmdline option to do this thing for dom0.
>> I think it would be better to unstatic disable_hpet() and call it
>> from Xen setup.  But as far as I can see hpet_init() should never be
>> called under Xen, because pv_time_ops won't be pointing to it, so
>> there won't be any attempt to use the hpet.
> Call disable_hpet() in dom0 xen setup phase will disable physical
> hpet and break hpet usage in hypervisor. There are another path to
> initialize hpet: fs_initcall(hpet_late_init),
> hpet_late_init()->hpet_enable(). 

Resend the updated patch which apply to pv-ops tree.

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 5eeeedb..f8a794b 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -285,6 +285,7 @@ void __init xen_arch_setup(void)
        memcpy(boot_command_line, xen_start_info->cmd_line,
+       strlcat(boot_command_line, " nohpet", COMMAND_LINE_SIZE);
        pm_idle = xen_idle;

Attachment: pv-dom0-nohpet.patch
Description: pv-dom0-nohpet.patch

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