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Subject[PATCH 10/13] KVM: Add the handler for Wake-up Vector
Date
When VCPU is blocked and an external interrupts from assigned
devices is delivered to it, VT-d Posted-Interrupts mechanism
will deliver a interrrupt to the associated physical CPU with
Wake-up Vector. In its handler, we find the destination VCPU
and wake up it.

Signed-off-by: Feng Wu <feng.wu@intel.com>
---
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/kvm/vmx.c | 52 +++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/x86.c | 22 +++++++++++-----
include/linux/kvm_host.h | 3 ++
virt/kvm/kvm_main.c | 3 ++
5 files changed, 75 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 71cfe3e..ca231a3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -99,6 +99,8 @@ static inline gfn_t gfn_to_index(gfn_t gfn, gfn_t base_gfn, int level)

#define ASYNC_PF_PER_VCPU 64

+extern void (*wakeup_handler_callback)(void);
+
enum kvm_reg {
VCPU_REGS_RAX = 0,
VCPU_REGS_RCX = 1,
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fa77714..51d2c8a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -822,6 +822,13 @@ 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;
@@ -2813,6 +2820,8 @@ 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
@@ -9183,6 +9192,7 @@ static int vmx_vcpu_pre_block(struct kvm_vcpu *vcpu)
struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
struct pi_desc old;
struct pi_desc new;
+ unsigned long flags;

if (!irq_post_enabled)
return 0;
@@ -9222,9 +9232,22 @@ static int vmx_vcpu_pre_block(struct kvm_vcpu *vcpu)

/* set 'NV' to 'wakeup vector' */
new.nv = POSTED_INTR_WAKEUP_VECTOR;
+
+ /*
+ * We should save physical cpu id here, vcpu->cpu may
+ * be changed due to preemption, in that case, this
+ * do-while loop will run again.
+ */
+ vcpu->wakeup_cpu = vcpu->cpu;
} while (cmpxchg(&pi_desc->control, old.control, new.control)
!= old.control);

+ spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,
+ vcpu->wakeup_cpu), flags);
+ list_add_tail(&vcpu->blocked_vcpu_list,
+ &per_cpu(blocked_vcpu_on_cpu, vcpu->wakeup_cpu));
+ spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,
+ vcpu->wakeup_cpu), flags);
return 0;
}

@@ -9234,6 +9257,7 @@ static void vmx_vcpu_post_block(struct kvm_vcpu *vcpu)
struct pi_desc old;
struct pi_desc new;
unsigned int dest = 0;
+ unsigned long flags;

if (!irq_post_enabled)
return;
@@ -9255,6 +9279,13 @@ static void vmx_vcpu_post_block(struct kvm_vcpu *vcpu)
} while (cmpxchg(&pi_desc->control, old.control, new.control)
!= old.control);

+ spin_lock_irqsave(&per_cpu(blocked_vcpu_on_cpu_lock,
+ vcpu->wakeup_cpu), flags);
+ list_del(&vcpu->blocked_vcpu_list);
+ spin_unlock_irqrestore(&per_cpu(blocked_vcpu_on_cpu_lock,
+ vcpu->wakeup_cpu), flags);
+ vcpu->wakeup_cpu = -1;
+
pi_clear_sn(pi_desc);
}

@@ -9372,6 +9403,25 @@ static struct kvm_x86_ops vmx_x86_ops = {
.vcpu_post_block = vmx_vcpu_post_block,
};

+/*
+ * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
+ */
+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 int __init vmx_init(void)
{
int r, i, msr;
@@ -9486,6 +9536,8 @@ static int __init vmx_init(void)

update_ple_window_actual_max();

+ wakeup_handler_callback = wakeup_handler;
+
return 0;

out7:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d0c8bb2..2061b3d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6156,6 +6156,21 @@ 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) {
@@ -6172,13 +6187,6 @@ 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);
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6bb8287..614b4ba 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -239,6 +239,9 @@ struct kvm_vcpu {
unsigned long requests;
unsigned long guest_debug;

+ int wakeup_cpu;
+ 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 1be1a45..fb3e504 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -224,6 +224,9 @@ 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->wakeup_cpu = -1;
+ INIT_LIST_HEAD(&vcpu->blocked_vcpu_list);
+
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
if (!page) {
r = -ENOMEM;
--
1.7.1


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