From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755118Ab1LGKt7 (ORCPT ); Wed, 7 Dec 2011 05:49:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57810 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754561Ab1LGKt5 (ORCPT ); Wed, 7 Dec 2011 05:49:57 -0500 Date: Wed, 7 Dec 2011 08:48:49 -0200 From: Marcelo Tosatti To: Raghavendra K T Cc: Greg Kroah-Hartman , KVM , Konrad Rzeszutek Wilk , Sedat Dilek , Virtualization , Jeremy Fitzhardinge , x86@kernel.org, "H. Peter Anvin" , Dave Jiang , Thomas Gleixner , Stefano Stabellini , Gleb Natapov , Yinghai Lu , Ingo Molnar , Avi Kivity , Rik van Riel , Xen , LKML , Srivatsa Vaddagiri , Peter Zijlstra , Sasha Levin , Suzuki Poulose , Dave Hansen Subject: Re: [PATCH RFC V3 2/4] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks Message-ID: <20111207104849.GA24849@amt.cnet> References: <20111130085921.23386.89708.sendpatchset@oc5400248562.ibm.com> <20111130085959.23386.69166.sendpatchset@oc5400248562.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111130085959.23386.69166.sendpatchset@oc5400248562.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 30, 2011 at 02:29:59PM +0530, 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_KICK_VCPU/KVM_CAP_KICK_VCPU. > > Qemu needs a corresponding patch to pass up the presence of this feature to > guest via cpuid. Patch to qemu will be sent separately. > > There is no Xen/KVM hypercall interface to await kick from. > > Signed-off-by: Srivatsa Vaddagiri > Signed-off-by: Suzuki Poulose > Signed-off-by: Raghavendra K T > --- > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index 734c376..8b1d65d 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_KICK_VCPU 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 c38efd7..6e1c8b4 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2103,6 +2103,7 @@ 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_KICK_VCPU: > r = 1; > break; > case KVM_CAP_COALESCED_MMIO: > @@ -2577,7 +2578,8 @@ 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_KICK_VCPU); > > if (sched_info_on()) > entry->eax |= (1 << KVM_FEATURE_STEAL_TIME); > @@ -5305,6 +5307,26 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) > return 1; > } > > +/* > + * kvm_pv_kick_cpu_op: Kick a vcpu. > + * > + * @cpu - vcpu to be kicked. > + */ > +static void kvm_pv_kick_cpu_op(struct kvm *kvm, int cpu) > +{ > + struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, cpu); > + struct kvm_mp_state mp_state; > + > + mp_state.mp_state = KVM_MP_STATE_RUNNABLE; Since vcpu->mp_state is not protected by a lock, this is potentially racy. For example: CPU0 CPU1 kvm_pv_kick_cpu_op running vcpuN vcpuN->mp_state = KVM_MP_STATE_RUNNABLE; kvm_emulate_halt vcpuN->mp_state = KVM_MP_STATE_HALTED Is it harmless to lose a kick?