On 09/04/2012 06:07 PM, Liu, Jinsong wrote: > From 728a17e2de591b557c3c8ba31076b4bf2ca5ab42 Mon Sep 17 00:00:00 2001 > From: Liu, Jinsong <jinsong.liu@xxxxxxxxx> > Date: Wed, 5 Sep 2012 03:18:15 +0800 > Subject: [PATCH] KVM: tsc deadline timer works only when hrtimer high resolution configured > > This is for 2 reasons: > 1. it's pointless to enable tsc deadline timer to guest when kernel hrtimer > not configured as high resolution, since that would be un-precise based on wheel; > 2. tsc deadline timer based on hrtimer, setting a leftmost node to rb tree > and then do hrtimer reprogram. If hrtimer not configured as high resolution, > hrtimer_enqueue_reprogram do nothing and would make tsc deadline timer fail. > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 148ed66..0e64997 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2210,7 +2210,11 @@ int kvm_dev_ioctl_check_extension(long ext) > r = kvm_has_tsc_control; > break; > case KVM_CAP_TSC_DEADLINE_TIMER: > +#ifdef CONFIG_HIGH_RES_TIMERS > r = boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER); > +#else > + r = 0; > +#endif > break; I prefer a patch making kvm for x86 depend on hrtimers. kvm already provides a high resolution timer to the guest in the local apic, backing it with the jiffies event source will likely cause some guests to malfunction. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
