On Thu, Dec 02, 2010 at 07:59:17AM -0600, Anthony Liguori wrote: > In certain use-cases, we want to allocate guests fixed time slices where idle > guest cycles leave the machine idling. There are many approaches to achieve > this but the most direct is to simply avoid trapping the HLT instruction which > lets the guest directly execute the instruction putting the processor to > sleep. > > Introduce this as a module-level option for kvm-vmx.ko since if you do this > for one guest, you probably want to do it for all. A similar option is > possible > for AMD but I don't have easy access to AMD test hardware. > > Signed-off-by: Anthony Liguori <aligu...@us.ibm.com> > --- > v1 -> v2 > - Rename parameter to yield_on_hlt > - Remove __read_mostly > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index caa967e..d8310e4 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -69,6 +69,9 @@ module_param(emulate_invalid_guest_state, bool, S_IRUGO); > static int __read_mostly vmm_exclusive = 1; > module_param(vmm_exclusive, bool, S_IRUGO); > > +static int yield_on_hlt = 1; > +module_param(yield_on_hlt, bool, S_IRUGO); > + > #define KVM_GUEST_CR0_MASK_UNRESTRICTED_GUEST > \ > (X86_CR0_WP | X86_CR0_NE | X86_CR0_NW | X86_CR0_CD) > #define KVM_GUEST_CR0_MASK \ > @@ -1419,7 +1422,7 @@ static __init int setup_vmcs_config(struct vmcs_config > *vmcs_conf) > &_pin_based_exec_control) < 0) > return -EIO; > > - min = CPU_BASED_HLT_EXITING | > + min = > #ifdef CONFIG_X86_64 > CPU_BASED_CR8_LOAD_EXITING | > CPU_BASED_CR8_STORE_EXITING | > @@ -1432,6 +1435,10 @@ static __init int setup_vmcs_config(struct vmcs_config > *vmcs_conf) > CPU_BASED_MWAIT_EXITING | > CPU_BASED_MONITOR_EXITING | > CPU_BASED_INVLPG_EXITING; > + > + if (yield_on_hlt) > + min |= CPU_BASED_HLT_EXITING; > + > opt = CPU_BASED_TPR_SHADOW | > CPU_BASED_USE_MSR_BITMAPS | > CPU_BASED_ACTIVATE_SECONDARY_CONTROLS; > -- > 1.7.0.4
Breaks async PF (see "checks on guest state"), timer reinjection probably. It should be possible to achieve determinism with a scheduler policy? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
