Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751616AbdFFK51 (ORCPT ); Tue, 6 Jun 2017 06:57:27 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35928 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751753AbdFFK5Z (ORCPT ); Tue, 6 Jun 2017 06:57:25 -0400 From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Longpeng , Huangweidong , Gonglei , wangxin , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= Subject: [PATCH 4/4] KVM: VMX: simplify cmpxchg of PI descriptor control field Date: Tue, 6 Jun 2017 12:57:07 +0200 Message-Id: <20170606105707.23207-5-pbonzini@redhat.com> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170606105707.23207-1-pbonzini@redhat.com> References: <20170606105707.23207-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4999 Lines: 166 Introduce new helpers __pi_set_ndst and pi_try_cmpxchg_control. Cc: Longpeng (Mike) Cc: Huangweidong Cc: Gonglei Cc: wangxin Cc: Radim Krčmář Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 83 ++++++++++++++++++++++++++---------------------------- 1 file changed, 40 insertions(+), 43 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 81047f373747..4f6b5fa57bbc 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -560,6 +560,29 @@ static inline int pi_test_sn(struct pi_desc *pi_desc) (unsigned long *)&pi_desc->control); } +/* Note that this is not an atomic operation. */ +static inline void __pi_set_ndst(struct pi_desc *pi_desc, unsigned cpu) +{ + unsigned dest = cpu_physical_id(cpu); + + if (x2apic_enabled()) + pi_desc->ndst = dest; + else + pi_desc->ndst = (dest << 8) & 0xFF00; +} + +static inline bool pi_try_cmpxchg_control(struct pi_desc *pi_desc, + struct pi_desc *old, + struct pi_desc *new) +{ + if (cmpxchg(&pi_desc->control, old->control, + new->control) == old->control) + return true; + + old->control = READ_ONCE(pi_desc->control); + return false; +} + struct vcpu_vmx { struct kvm_vcpu vcpu; unsigned long host_rsp; @@ -2182,7 +2205,6 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) { struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); struct pi_desc old, new; - unsigned int dest; /* * In case of hot-plug or hot-unplug, we may have to undo @@ -2209,19 +2231,12 @@ static void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu) } /* The full case. */ + old.control = pi_desc->control; do { - old.control = new.control = pi_desc->control; - - dest = cpu_physical_id(cpu); - - if (x2apic_enabled()) - new.ndst = dest; - else - new.ndst = (dest << 8) & 0xFF00; - + new.control = old.control; + __pi_set_ndst(&new, cpu); new.sn = 0; - } while (cmpxchg(&pi_desc->control, old.control, - new.control) != old.control); + } while (!pi_try_cmpxchg_control(pi_desc, &old, &new)); } static void decache_tsc_multiplier(struct vcpu_vmx *vmx) @@ -11240,24 +11255,16 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) { struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); struct pi_desc old, new; - unsigned int dest; + old.control = pi_desc->control; do { - old.control = new.control = pi_desc->control; WARN(old.nv != POSTED_INTR_WAKEUP_VECTOR, "Wakeup handler not enabled while the VCPU is blocked\n"); - dest = cpu_physical_id(vcpu->cpu); - - if (x2apic_enabled()) - new.ndst = dest; - else - new.ndst = (dest << 8) & 0xFF00; - - /* set 'NV' to 'notification vector' */ + new.control = old.control; + __pi_set_ndst(&new, vcpu->cpu); new.nv = POSTED_INTR_VECTOR; - } while (cmpxchg(&pi_desc->control, old.control, - new.control) != old.control); + } while (!pi_try_cmpxchg_control(pi_desc, &old, &new)); if (!WARN_ON_ONCE(vcpu->pre_pcpu == -1)) { spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); @@ -11265,6 +11272,7 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); vcpu->pre_pcpu = -1; } + } /* @@ -11282,7 +11290,6 @@ static void __pi_post_block(struct kvm_vcpu *vcpu) */ static int pi_pre_block(struct kvm_vcpu *vcpu) { - unsigned int dest; struct pi_desc old, new; struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); @@ -11302,32 +11309,22 @@ static int pi_pre_block(struct kvm_vcpu *vcpu) spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, vcpu->pre_pcpu)); } + old.control = pi_desc->control; do { - old.control = new.control = pi_desc->control; - WARN((pi_desc->sn == 1), "Warning: SN field of posted-interrupts " "is set before blocking\n"); /* - * Since vCPU can be preempted during this process, - * vcpu->cpu could be different with pre_pcpu, we - * need to set pre_pcpu as the destination of wakeup - * notification event, then we can find the right vCPU - * to wakeup in wakeup handler if interrupts happen - * when the vCPU is in blocked state. + * The wakeup_handler expects the VCPU to be on the + * blocked_vcpu_list that matches ndst. Interrupts + * are disabled so no preemption should happen, but + * err on the side of safety. */ - dest = cpu_physical_id(vcpu->pre_pcpu); - - if (x2apic_enabled()) - new.ndst = dest; - else - new.ndst = (dest << 8) & 0xFF00; - - /* set 'NV' to 'wakeup vector' */ + new.control = old.control; + __pi_set_ndst(&new, vcpu->pre_pcpu); new.nv = POSTED_INTR_WAKEUP_VECTOR; - } while (cmpxchg(&pi_desc->control, old.control, - new.control) != old.control); + } while (!pi_try_cmpxchg_control(pi_desc, &old, &new)); /* We should not block the vCPU if an interrupt is posted for it. */ if (pi_test_on(pi_desc) == 1) -- 2.13.0