[v4 15/16] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked

Feng Wu
2015-06-11T11:03:50Z

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

Signed-off-by: Feng Wu <feng.wu@intel.com>
---
arch/x86/include/asm/kvm_host.h | 3 +
arch/x86/kvm/vmx.c | 158 ++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 42 ++++++++---
include/linux/kvm_host.h | 3 +
virt/kvm/kvm_main.c | 3 +
5 files changed, 199 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1605bf8..2ef6f2a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -842,6 +842,9 @@ struct kvm_x86_ops {

void (*pi_clear_sn)(struct kvm_vcpu *vcpu);
void (*pi_set_sn)(struct kvm_vcpu *vcpu);
+
+ int (*pi_pre_block)(struct kvm_vcpu *vcpu);
+ void (*pi_post_block)(struct kvm_vcpu *vcpu);
};

struct kvm_arch_async_pf {
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9d9b403..7e8a800 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -888,6 +888,13 @@ 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;
@@ -2972,6 +2979,8 @@ 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
@@ -6099,6 +6108,25 @@ 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;
@@ -6283,6 +6311,8 @@ 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:
@@ -10236,6 +10266,131 @@ static void vmx_enable_log_dirty_pt_masked(struct kvm *kvm,
kvm_mmu_clear_dirty_pt_masked(kvm, memslot, offset, mask);
}

+/*
+ * 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_pi_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 (!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_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;
+ unsigned long flags;
+
+ if (!irq_remapping_cap(IRQ_POSTING_CAP))
+ return;
+
+ /*
+ * If the vCPU is not really blocked and vmx_vcpu_load()
+ * doesn't have chance to run before this point, we should
+ * set posted-interrupt descriptor back, just like what we
+ * do in vmx_vcpu_load().
+ */
+ if (pi_desc->nv == POSTED_INTR_WAKEUP_VECTOR)
+ 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;
+ }
+}
+
static struct kvm_x86_ops vmx_x86_ops = {
.cpu_has_kvm_support = cpu_has_kvm_support,
.disabled_by_bios = vmx_disabled_by_bios,
@@ -10354,6 +10509,9 @@ static struct kvm_x86_ops vmx_x86_ops = {

.pi_clear_sn = vmx_pi_clear_sn,
.pi_set_sn = vmx_pi_set_sn,
+
+ .pi_pre_block = vmx_pi_pre_block,
+ .pi_post_block = vmx_pi_post_block,
};

static int __init vmx_init(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c73efcd..fabf4a7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5866,7 +5866,11 @@ 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->pi_pre_block ||
+ (kvm_x86_ops->pi_pre_block &&
+ kvm_x86_ops->pi_pre_block(vcpu) == 0))
+ vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
return 1;
} else {
vcpu->run->exit_reason = KVM_EXIT_HLT;
@@ -6282,6 +6286,21 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_vcpu_reload_apic_access_page(vcpu);
}

+ /*
+ * Since posted-interrupts can be set by VT-d HW now, in this
+ * case, KVM_REQ_EVENT is not set. We move the following
+ * operations out of the if statement.
+ */
+ 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) {
@@ -6298,13 +6317,6 @@ 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);
}
@@ -6475,10 +6487,20 @@ 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) {
r = vcpu_enter_guest(vcpu);
- else
+ } else {
r = vcpu_block(kvm, vcpu);
+
+ /*
+ * pi_post_block() must be called after
+ * pi_pre_block() which is called in
+ * kvm_vcpu_halt().
+ */
+ if (kvm_x86_ops->pi_post_block)
+ kvm_x86_ops->pi_post_block(vcpu);
+ }
+
if (r <= 0)
break;

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 69f8711..6c90ef2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -225,6 +225,9 @@ 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 9097741..6938554 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -221,6 +221,9 @@ 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