Re: [PATCH RFC V4 2/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

[Alexander Graf <agraf@suse.de>]

On 14.01.2012, at 19:25, Raghavendra K T wrote:

> Add a hypercall to KVM hypervisor to support pv-ticketlocks 
> 
> KVM_HC_KICK_CPU allows the calling vcpu to kick another vcpu out of halt state.
> 
> The presence of these hypercalls is indicated to guest via
> KVM_FEATURE_PVLOCK_KICK/KVM_CAP_PVLOCK_KICK.
> 
> Qemu needs a corresponding patch to pass up the presence of this feature to 
> guest via cpuid. Patch to qemu will be sent separately.
> 
> Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
> Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com>
> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
> ---
> diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
> index 734c376..7a94987 100644
> --- a/arch/x86/include/asm/kvm_para.h
> +++ b/arch/x86/include/asm/kvm_para.h
> @@ -16,12 +16,14 @@
> #define KVM_FEATURE_CLOCKSOURCE		0
> #define KVM_FEATURE_NOP_IO_DELAY	1
> #define KVM_FEATURE_MMU_OP		2
> +
> /* This indicates that the new set of kvmclock msrs
>  * are available. The use of 0x11 and 0x12 is deprecated
>  */
> #define KVM_FEATURE_CLOCKSOURCE2        3
> #define KVM_FEATURE_ASYNC_PF		4
> #define KVM_FEATURE_STEAL_TIME		5
> +#define KVM_FEATURE_PVLOCK_KICK		6
> 
> /* The last 8 bits are used to indicate how to interpret the flags field
>  * in pvclock structure. If no bits are set, all flags are ignored.
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4c938da..c7b05fc 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2099,6 +2099,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> 	case KVM_CAP_XSAVE:
> 	case KVM_CAP_ASYNC_PF:
> 	case KVM_CAP_GET_TSC_KHZ:
> +	case KVM_CAP_PVLOCK_KICK:
> 		r = 1;
> 		break;
> 	case KVM_CAP_COALESCED_MMIO:
> @@ -2576,7 +2577,8 @@ static void do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> 			     (1 << KVM_FEATURE_NOP_IO_DELAY) |
> 			     (1 << KVM_FEATURE_CLOCKSOURCE2) |
> 			     (1 << KVM_FEATURE_ASYNC_PF) |
> -			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
> +			     (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
> +			     (1 << KVM_FEATURE_PVLOCK_KICK);
> 
> 		if (sched_info_on())
> 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
> @@ -5304,6 +5306,29 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
> 	return 1;
> }
> 
> +/*
> + * kvm_pv_kick_cpu_op:  Kick a vcpu.
> + *
> + * @apicid - apicid of vcpu to be kicked.
> + */
> +static void kvm_pv_kick_cpu_op(struct kvm *kvm, int apicid)
> +{
> +	struct kvm_vcpu *vcpu = NULL;
> +	int i;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		if (!kvm_apic_present(vcpu))
> +			continue;
> +
> +		if (kvm_apic_match_dest(vcpu, 0, 0, apicid, 0))
> +			break;
> +	}
> +	if (vcpu) {
> +		kvm_make_request(KVM_REQ_PVLOCK_KICK, vcpu);
> +		kvm_vcpu_kick(vcpu);
> +	}
> +}
> +
> int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> {
> 	unsigned long nr, a0, a1, a2, a3, ret;
> @@ -5340,6 +5365,10 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> 	case KVM_HC_MMU_OP:
> 		r = kvm_pv_mmu_op(vcpu, a0, hc_gpa(vcpu, a1, a2), &ret);
> 		break;
> +	case KVM_HC_KICK_CPU:
> +		kvm_pv_kick_cpu_op(vcpu->kvm, a0);
> +		ret = 0;
> +		break;
> 	default:
> 		ret = -KVM_ENOSYS;
> 		break;
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index 68e67e5..63fb6b0 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -558,6 +558,7 @@ struct kvm_ppc_pvinfo {
> #define KVM_CAP_PPC_PAPR 68
> #define KVM_CAP_S390_GMAP 71
> #define KVM_CAP_TSC_DEADLINE_TIMER 72
> +#define KVM_CAP_PVLOCK_KICK 73
> 
> #ifdef KVM_CAP_IRQ_ROUTING
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d526231..3b1ae7b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -50,6 +50,7 @@
> #define KVM_REQ_APF_HALT          12
> #define KVM_REQ_STEAL_UPDATE      13
> #define KVM_REQ_NMI               14
> +#define KVM_REQ_PVLOCK_KICK       15

Everything I see in this patch is pvlock agnostic. It's only a vcpu kick hypercall. So it's probably a good idea to also name it accordingly :).


Alex