Re: [Xen-devel] 2.6.37 dom0 under Xen 4.1 clocksource not working

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jan 26, 2011 at 05:07:27PM +0000, Stefano Stabellini wrote:
> On Wed, 26 Jan 2011, Daniel De Graaf wrote:
> > On 01/26/2011 10:40 AM, Jeremy Fitzhardinge wrote:
> > > On 01/10/2011 07:06 AM, Daniel De Graaf wrote:
> > >> When booting 2.6.37 (from kernel.org) under Xen 4.1, there are
> > >> apparently issues with timer interrupts being delivered to the dom0.
> > >> Repeatedly causing an interrupt (for example, the ACPI power button) will
> > >> allow the system to boot, as does adding "clocksource=jiffies" to the
> > >> kernel command line. This is only present under Xen, not when booting the
> > >> same kernel on real hardware.
> > > 
> > > Ah, yes.  This is from the cpuidle stuff, I think.  Does booting with
> > > "idle=halt" work?
> > > 
> > 
> > Yes, clocksource=xen idle=halt works.
> 
> I have a testbox that can reproduce this problem.
> It seems to be caused by the cpuidle driver that overrides pm_idle
> unless boot_option_idle_override is set to something other than the
> default.
> This patch fixes the problem for me:
> 
> ---
> 
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index a3d28a1..7e85979 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -353,6 +353,7 @@ void __init xen_arch_setup(void)
>       boot_cpu_data.hlt_works_ok = 1;
>  #endif
>       pm_idle = default_idle;
> +     boot_option_idle_override = IDLE_HALT;

Is this how 2.6.32 did it? Or was there no cpuidle driver in 2.6.32 so
we never had tried this? With this being overwridden to HALT does that
mean the hypervisor cycles through the Cx states? What about using
MWAIT instead? How does this impact AMD platforms?

>  
>       fiddle_vdso();
>  }
> 
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