> -----Original Message----- > From: David Matlack [mailto:dmatlack@xxxxxxxxxx] > Sent: Thursday, October 15, 2015 7:41 AM > To: Wu, Feng <feng.wu@xxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>; alex.williamson@xxxxxxxxxx; Joerg > Roedel <joro@xxxxxxxxxx>; Marcelo Tosatti <mtosatti@xxxxxxxxxx>; > eric.auger@xxxxxxxxxx; kvm list <kvm@xxxxxxxxxxxxxxx>; iommu@lists.linux- > foundation.org; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v9 17/18] KVM: Update Posted-Interrupts Descriptor when > vCPU is blocked > > Hi Feng. > > On Fri, Sep 18, 2015 at 7:29 AM, Feng Wu <feng.wu@xxxxxxxxx> wrote: > > This patch updates the Posted-Interrupts Descriptor when vCPU > > is blocked. > > > > pre-block: > > - Add the vCPU to the blocked per-CPU list > > - Set 'NV' to POSTED_INTR_WAKEUP_VECTOR > > > > post-block: > > - Remove the vCPU from the per-CPU list > > I'm wondering what happens if a posted interrupt arrives at the IOMMU > after pre-block and before post-block. > > In pre_block, NV is set to POSTED_INTR_WAKEUP_VECTOR. IIUC, this means > future posted interrupts will not trigger "Posted-Interrupt Processing" > (PIR will not get copied to VIRR). Instead, the IOMMU will do ON := 1, > PIR |= (1 << vector), and send POSTED_INTR_WAKEUP_VECTOR. PIWV calls > wakeup_handler which does kvm_vcpu_kick. kvm_vcpu_kick does a wait-queue > wakeup and possibly a scheduler ipi. > > But the VCPU is sitting in kvm_vcpu_block. It spins and/or schedules > (wait queue) until it has a reason to wake up. I couldn't find a code > path from kvm_vcpu_block that lead to checking ON or PIR. How does the > blocked VCPU "receive" the posted interrupt? (And when does Posted- > Interrupt Processing get triggered?) In the pre_block, it also change the 'NDST' filed to the pCPU, on which the vCPU is put to the per-CPU list 'blocked_vcpu_on_cpu', so when posted-interrupts come it, it will sent the wakeup notification event to the pCPU above, then in the wakeup_handler, it can find the vCPU from the per-CPU list, hence kvm_vcpu_kick can wake up it. Thanks, Feng > > Thanks! > > > > > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx> > > --- > > v9: > > - Add description for blocked_vcpu_on_cpu_lock in > Documentation/virtual/kvm/locking.txt > > - Check !kvm_arch_has_assigned_device(vcpu->kvm) first, then > > !irq_remapping_cap(IRQ_POSTING_CAP) > > > > v8: > > - Rename 'pi_pre_block' to 'pre_block' > > - Rename 'pi_post_block' to 'post_block' > > - Change some comments > > - Only add the vCPU to the blocking list when the VM has assigned devices. > > > > Documentation/virtual/kvm/locking.txt | 12 +++ > > arch/x86/include/asm/kvm_host.h | 13 +++ > > arch/x86/kvm/vmx.c | 153 > ++++++++++++++++++++++++++++++++++ > > arch/x86/kvm/x86.c | 53 +++++++++--- > > include/linux/kvm_host.h | 3 + > > virt/kvm/kvm_main.c | 3 + > > 6 files changed, 227 insertions(+), 10 deletions(-) > > > > diff --git a/Documentation/virtual/kvm/locking.txt > b/Documentation/virtual/kvm/locking.txt > > index d68af4d..19f94a6 100644 > > --- a/Documentation/virtual/kvm/locking.txt > > +++ b/Documentation/virtual/kvm/locking.txt > > @@ -166,3 +166,15 @@ Comment: The srcu read lock must be held while > accessing memslots (e.g. > > MMIO/PIO address->device structure mapping (kvm->buses). > > The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu > > if it is needed by multiple functions. > > + > > +Name: blocked_vcpu_on_cpu_lock > > +Type: spinlock_t > > +Arch: x86 > > +Protects: blocked_vcpu_on_cpu > > +Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts. > > + When VT-d posted-interrupts is supported and the VM has assigned > > + devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu > > + protected by blocked_vcpu_on_cpu_lock, when VT-d hardware > issues > > + wakeup notification event since external interrupts from the > > + assigned devices happens, we will find the vCPU on the list to > > + wakeup. > > diff --git a/arch/x86/include/asm/kvm_host.h > b/arch/x86/include/asm/kvm_host.h > > index 0ddd353..304fbb5 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -552,6 +552,8 @@ struct kvm_vcpu_arch { > > */ > > bool write_fault_to_shadow_pgtable; > > > > + bool halted; > > + > > /* set at EPT violation at this point */ > > unsigned long exit_qualification; > > > > @@ -864,6 +866,17 @@ struct kvm_x86_ops { > > /* pmu operations of sub-arch */ > > const struct kvm_pmu_ops *pmu_ops; > > > > + /* > > + * Architecture specific hooks for vCPU blocking due to > > + * HLT instruction. > > + * Returns for .pre_block(): > > + * - 0 means continue to block the vCPU. > > + * - 1 means we cannot block the vCPU since some event > > + * happens during this period, such as, 'ON' bit in > > + * posted-interrupts descriptor is set. > > + */ > > + int (*pre_block)(struct kvm_vcpu *vcpu); > > + void (*post_block)(struct kvm_vcpu *vcpu); > > int (*update_pi_irte)(struct kvm *kvm, unsigned int host_irq, > > uint32_t guest_irq, bool set); > > }; > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > index 902a67d..9968896 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -879,6 +879,13 @@ static DEFINE_PER_CPU(struct vmcs *, > current_vmcs); > > static DEFINE_PER_CPU(struct list_head, loaded_vmcss_on_cpu); > > static DEFINE_PER_CPU(struct desc_ptr, host_gdt); > > > > +/* > > + * We maintian a per-CPU linked-list of vCPU, so in wakeup_handler() we > > + * can find which vCPU should be waken up. > > + */ > > +static DEFINE_PER_CPU(struct list_head, blocked_vcpu_on_cpu); > > +static DEFINE_PER_CPU(spinlock_t, blocked_vcpu_on_cpu_lock); > > + > > static unsigned long *vmx_io_bitmap_a; > > static unsigned long *vmx_io_bitmap_b; > > static unsigned long *vmx_msr_bitmap_legacy; > > @@ -2985,6 +2992,8 @@ static int hardware_enable(void) > > return -EBUSY; > > > > INIT_LIST_HEAD(&per_cpu(loaded_vmcss_on_cpu, cpu)); > > + INIT_LIST_HEAD(&per_cpu(blocked_vcpu_on_cpu, cpu)); > > + spin_lock_init(&per_cpu(blocked_vcpu_on_cpu_lock, cpu)); > > > > /* > > * Now we can enable the vmclear operation in kdump > > @@ -6121,6 +6130,25 @@ static void update_ple_window_actual_max(void) > > ple_window_grow, INT_MIN); > > } > > > > +/* > > + * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR. > > + */ > > +static void wakeup_handler(void) > > +{ > > + struct kvm_vcpu *vcpu; > > + int cpu = smp_processor_id(); > > + > > + spin_lock(&per_cpu(blocked_vcpu_on_cpu_lock, cpu)); > > + list_for_each_entry(vcpu, &per_cpu(blocked_vcpu_on_cpu, cpu), > > + blocked_vcpu_list) { > > + struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); > > + > > + if (pi_test_on(pi_desc) == 1) > > + kvm_vcpu_kick(vcpu); > > + } > > + spin_unlock(&per_cpu(blocked_vcpu_on_cpu_lock, cpu)); > > +} > > + > > static __init int hardware_setup(void) > > { > > int r = -ENOMEM, i, msr; > > @@ -6305,6 +6333,8 @@ static __init int hardware_setup(void) > > kvm_x86_ops->enable_log_dirty_pt_masked = NULL; > > } > > > > + kvm_set_posted_intr_wakeup_handler(wakeup_handler); > > + > > return alloc_kvm_area(); > > > > out8: > > @@ -10430,6 +10460,126 @@ static void > vmx_enable_log_dirty_pt_masked(struct kvm *kvm, > > } > > > > /* > > + * This routine does the following things for vCPU which is going > > + * to be blocked if VT-d PI is enabled. > > + * - Store the vCPU to the wakeup list, so when interrupts happen > > + * we can find the right vCPU to wake up. > > + * - Change the Posted-interrupt descriptor as below: > > + * 'NDST' <-- vcpu->pre_pcpu > > + * 'NV' <-- POSTED_INTR_WAKEUP_VECTOR > > + * - If 'ON' is set during this process, which means at least one > > + * interrupt is posted for this vCPU, we cannot block it, in > > + * this case, return 1, otherwise, return 0. > > + * > > + */ > > +static int vmx_pre_block(struct kvm_vcpu *vcpu) > > +{ > > + unsigned long flags; > > + unsigned int dest; > > + struct pi_desc old, new; > > + struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); > > + > > + if (!kvm_arch_has_assigned_device(vcpu->kvm) || > > + !irq_remapping_cap(IRQ_POSTING_CAP)) > > + return 0; > > + > > + vcpu->pre_pcpu = vcpu->cpu; > > + spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + list_add_tail(&vcpu->blocked_vcpu_list, > > + &per_cpu(blocked_vcpu_on_cpu, > > + vcpu->pre_pcpu)); > > + spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + > > + do { > > + old.control = new.control = pi_desc->control; > > + > > + /* > > + * We should not block the vCPU if > > + * an interrupt is posted for it. > > + */ > > + if (pi_test_on(pi_desc) == 1) { > > + spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + list_del(&vcpu->blocked_vcpu_list); > > + spin_unlock_irqrestore( > > + &per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + vcpu->pre_pcpu = -1; > > + > > + return 1; > > + } > > + > > + 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. > > + */ > > + 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.nv = POSTED_INTR_WAKEUP_VECTOR; > > + } while (cmpxchg(&pi_desc->control, old.control, > > + new.control) != old.control); > > + > > + return 0; > > +} > > + > > +static void vmx_post_block(struct kvm_vcpu *vcpu) > > +{ > > + struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu); > > + struct pi_desc old, new; > > + unsigned int dest; > > + unsigned long flags; > > + > > + if (!kvm_arch_has_assigned_device(vcpu->kvm) || > > + !irq_remapping_cap(IRQ_POSTING_CAP)) > > + return; > > + > > + do { > > + old.control = new.control = pi_desc->control; > > + > > + dest = cpu_physical_id(vcpu->cpu); > > + > > + if (x2apic_enabled()) > > + new.ndst = dest; > > + else > > + new.ndst = (dest << 8) & 0xFF00; > > + > > + /* Allow posting non-urgent interrupts */ > > + new.sn = 0; > > + > > + /* set 'NV' to 'notification vector' */ > > + new.nv = POSTED_INTR_VECTOR; > > + } while (cmpxchg(&pi_desc->control, old.control, > > + new.control) != old.control); > > + > > + if(vcpu->pre_pcpu != -1) { > > + spin_lock_irqsave( > > + &per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + list_del(&vcpu->blocked_vcpu_list); > > + spin_unlock_irqrestore( > > + &per_cpu(blocked_vcpu_on_cpu_lock, > > + vcpu->pre_pcpu), flags); > > + vcpu->pre_pcpu = -1; > > + } > > +} > > + > > +/* > > * vmx_update_pi_irte - set IRTE for Posted-Interrupts > > * > > * @kvm: kvm > > @@ -10620,6 +10770,9 @@ static struct kvm_x86_ops vmx_x86_ops = { > > .flush_log_dirty = vmx_flush_log_dirty, > > .enable_log_dirty_pt_masked = vmx_enable_log_dirty_pt_masked, > > > > + .pre_block = vmx_pre_block, > > + .post_block = vmx_post_block, > > + > > .pmu_ops = &intel_pmu_ops, > > > > .update_pi_irte = vmx_update_pi_irte, > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 58688aa..46f55b2 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -5869,7 +5869,12 @@ int kvm_vcpu_halt(struct kvm_vcpu *vcpu) > > { > > ++vcpu->stat.halt_exits; > > if (irqchip_in_kernel(vcpu->kvm)) { > > - vcpu->arch.mp_state = KVM_MP_STATE_HALTED; > > + /* Handle posted-interrupt when vCPU is to be halted */ > > + if (!kvm_x86_ops->pre_block || > > + kvm_x86_ops->pre_block(vcpu) == 0) { > > + vcpu->arch.halted = true; > > + vcpu->arch.mp_state = KVM_MP_STATE_HALTED; > > + } > > return 1; > > } else { > > vcpu->run->exit_reason = KVM_EXIT_HLT; > > @@ -6518,6 +6523,20 @@ static int vcpu_enter_guest(struct kvm_vcpu > *vcpu) > > kvm_vcpu_reload_apic_access_page(vcpu); > > } > > > > + /* > > + * KVM_REQ_EVENT is not set when posted interrupts are set by > > + * VT-d hardware, so we have to update RVI unconditionally. > > + */ > > + if (kvm_lapic_enabled(vcpu)) { > > + /* > > + * Update architecture specific hints for APIC > > + * virtual interrupt delivery. > > + */ > > + if (kvm_x86_ops->hwapic_irr_update) > > + kvm_x86_ops->hwapic_irr_update(vcpu, > > + kvm_lapic_find_highest_irr(vcpu)); > > + } > > + > > if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) { > > kvm_apic_accept_events(vcpu); > > if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) { > > @@ -6534,13 +6553,6 @@ static int vcpu_enter_guest(struct kvm_vcpu > *vcpu) > > kvm_x86_ops->enable_irq_window(vcpu); > > > > if (kvm_lapic_enabled(vcpu)) { > > - /* > > - * Update architecture specific hints for APIC > > - * virtual interrupt delivery. > > - */ > > - if (kvm_x86_ops->hwapic_irr_update) > > - kvm_x86_ops->hwapic_irr_update(vcpu, > > - kvm_lapic_find_highest_irr(vcpu)); > > update_cr8_intercept(vcpu); > > kvm_lapic_sync_to_vapic(vcpu); > > } > > @@ -6711,10 +6723,31 @@ static int vcpu_run(struct kvm_vcpu *vcpu) > > > > for (;;) { > > if (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE && > > - !vcpu->arch.apf.halted) > > + !vcpu->arch.apf.halted) { > > + /* > > + * For some cases, we can get here with > > + * vcpu->arch.halted being true. > > + */ > > + if (kvm_x86_ops->post_block && vcpu->arch.halted) { > > + kvm_x86_ops->post_block(vcpu); > > + vcpu->arch.halted = false; > > + } > > + > > r = vcpu_enter_guest(vcpu); > > - else > > + } else { > > r = vcpu_block(kvm, vcpu); > > + > > + /* > > + * post_block() must be called after > > + * pre_block() which is called in > > + * kvm_vcpu_halt(). > > + */ > > + if (kvm_x86_ops->post_block && vcpu->arch.halted) { > > + kvm_x86_ops->post_block(vcpu); > > + vcpu->arch.halted = false; > > + } > > + } > > + > > if (r <= 0) > > break; > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index feba1fb..bf462e7 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -231,6 +231,9 @@ struct kvm_vcpu { > > unsigned long requests; > > unsigned long guest_debug; > > > > + int pre_pcpu; > > + struct list_head blocked_vcpu_list; > > + > > struct mutex mutex; > > struct kvm_run *run; > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 8b8a444..191c7eb 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -220,6 +220,9 @@ int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm > *kvm, unsigned id) > > init_waitqueue_head(&vcpu->wq); > > kvm_async_pf_vcpu_init(vcpu); > > > > + vcpu->pre_pcpu = -1; > > + INIT_LIST_HEAD(&vcpu->blocked_vcpu_list); > > + > > page = alloc_page(GFP_KERNEL | __GFP_ZERO); > > if (!page) { > > r = -ENOMEM; > > -- > > 2.1.0 > > > > -- > > 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 ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
