[3/4] KVM: introduce irq_lock, use it protect ioapic

Commit Message

Marcelo Tosatti May 18, 2009, 4:56 p.m. UTC

Signed-off-by: Marcelo Tosatti <[e-mail]>

Comments

Avi Kivity May 20, 2009, 12:11 p.m. UTC | #1

Marcelo Tosatti wrote:
> Signed-off-by: Marcelo Tosatti <[e-mail]>
>
> Index: kvm/include/linux/kvm_host.h
> ===================================================================
> --- kvm.orig/include/linux/kvm_host.h
> +++ kvm/include/linux/kvm_host.h
> @@ -123,7 +123,6 @@ struct kvm_kernel_irq_routing_entry {
>  };
>  
>  struct kvm {
> -	struct mutex lock; /* protects the vcpus array and APIC accesses */
>   

Why move?

Marcelo Tosatti May 20, 2009, 2:11 p.m. UTC | #2

On Wed, May 20, 2009 at 03:11:35PM +0300, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> Signed-off-by: Marcelo Tosatti <[e-mail]>
>>
>> Index: kvm/include/linux/kvm_host.h
>> ===================================================================
>> --- kvm.orig/include/linux/kvm_host.h
>> +++ kvm/include/linux/kvm_host.h
>> @@ -123,7 +123,6 @@ struct kvm_kernel_irq_routing_entry {
>>  };
>>   struct kvm {
>> -	struct mutex lock; /* protects the vcpus array and APIC accesses */
>>   
>
> Why move?

To have it close to the data it protects, for readability. Need to
pahole and organize it at some point.


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Avi Kivity May 20, 2009, 2:29 p.m. UTC | #3

Marcelo Tosatti wrote:
> On Wed, May 20, 2009 at 03:11:35PM +0300, Avi Kivity wrote:
>   
>> Marcelo Tosatti wrote:
>>     
>>> Signed-off-by: Marcelo Tosatti <[e-mail]>
>>>
>>> Index: kvm/include/linux/kvm_host.h
>>> ===================================================================
>>> --- kvm.orig/include/linux/kvm_host.h
>>> +++ kvm/include/linux/kvm_host.h
>>> @@ -123,7 +123,6 @@ struct kvm_kernel_irq_routing_entry {
>>>  };
>>>   struct kvm {
>>> -	struct mutex lock; /* protects the vcpus array and APIC accesses */
>>>   
>>>       
>> Why move?
>>     
>
> To have it close to the data it protects, for readability. Need to
> pahole and organize it at some point.
>
>   

Ok.

Patch

Index: kvm/include/linux/kvm_host.h
===================================================================
--- kvm.orig/include/linux/kvm_host.h
+++ kvm/include/linux/kvm_host.h
@@ -123,7 +123,6 @@  struct kvm_kernel_irq_routing_entry {
 };
 
 struct kvm {
-	struct mutex lock; /* protects the vcpus array and APIC accesses */
 	spinlock_t mmu_lock;
 	struct rw_semaphore slots_lock;
 	struct mm_struct *mm; /* userspace tied to this vm */
@@ -132,6 +131,12 @@  struct kvm {
 					KVM_PRIVATE_MEM_SLOTS];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 	struct list_head vm_list;
+	struct mutex lock; /*
+			    * - protects mmio_bus, pio_bus.
+			    * - protects a few concurrent ioctl's (FIXME).
+			    * - protects concurrent create_vcpu, but
+			    *   kvm->vcpus walkers do it locklessly (FIXME).
+			    */
 	struct kvm_io_bus mmio_bus;
 	struct kvm_io_bus pio_bus;
 	struct kvm_vm_stat stat;
@@ -142,6 +147,7 @@  struct kvm {
 	struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
 #endif
 
+	struct mutex irq_lock; /* protects high level irq logic, ioapic */
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 	struct list_head irq_routing; /* of kvm_kernel_irq_routing_entry */
 	struct hlist_head mask_notifier_list;
Index: kvm/virt/kvm/ioapic.c
===================================================================
--- kvm.orig/virt/kvm/ioapic.c
+++ kvm/virt/kvm/ioapic.c
@@ -225,6 +225,10 @@  static int ioapic_in_range(struct kvm_io
 {
 	struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;
 
+	/*
+	 * Lockless check for ioapic->base_address on the hazy assumption
+	 * it does not change during the lifetime of a VM.
+	 */
 	return ((addr >= ioapic->base_address &&
 		 (addr < ioapic->base_address + IOAPIC_MEM_LENGTH)));
 }
@@ -238,6 +242,7 @@  static void ioapic_mmio_read(struct kvm_
 	ioapic_debug("addr %lx\n", (unsigned long)addr);
 	ASSERT(!(addr & 0xf));	/* check alignment */
 
+	mutex_lock(&ioapic->kvm->irq_lock);
 	addr &= 0xff;
 	switch (addr) {
 	case IOAPIC_REG_SELECT:
@@ -264,6 +269,7 @@  static void ioapic_mmio_read(struct kvm_
 	default:
 		printk(KERN_WARNING "ioapic: wrong length %d\n", len);
 	}
+	mutex_unlock(&ioapic->kvm->irq_lock);
 }
 
 static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
@@ -275,6 +281,8 @@  static void ioapic_mmio_write(struct kvm
 	ioapic_debug("ioapic_mmio_write addr=%p len=%d val=%p\n",
 		     (void*)addr, len, val);
 	ASSERT(!(addr & 0xf));	/* check alignment */
+
+	mutex_lock(&ioapic->kvm->irq_lock);
 	if (len == 4 || len == 8)
 		data = *(u32 *) val;
 	else {
@@ -300,6 +308,7 @@  static void ioapic_mmio_write(struct kvm
 	default:
 		break;
 	}
+	mutex_unlock(&ioapic->kvm->irq_lock);
 }
 
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
Index: kvm/virt/kvm/kvm_main.c
===================================================================
--- kvm.orig/virt/kvm/kvm_main.c
+++ kvm/virt/kvm/kvm_main.c
@@ -984,6 +984,7 @@  static struct kvm *kvm_create_vm(void)
 	spin_lock_init(&kvm->mmu_lock);
 	kvm_io_bus_init(&kvm->pio_bus);
 	mutex_init(&kvm->lock);
+	mutex_init(&kvm->irq_lock);
 	kvm_io_bus_init(&kvm->mmio_bus);
 	init_rwsem(&kvm->slots_lock);
 	atomic_set(&kvm->users_count, 1);