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Commit 4a937f96 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: protect kvm_usage_count with its own spinlock 



The VM list need not be protected by a raw spinlock.  Separate the
two so that kvm_lock can be made non-raw.

Cc: kvm@vger.kernel.org
Cc: gleb@redhat.com
Cc: jan.kiszka@siemens.com
Reviewed-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4fa92fb2

Documentation/virtual/kvm/locking.txt

+5 −1
Original line number Diff line number Diff line
@@ -135,7 +135,11 @@ Name: kvm_lock 
Type:		raw_spinlock

Arch:		any

Protects:	- vm_list

		- hardware virtualization enable/disable



Name:		kvm_count_lock

Type:		raw_spinlock_t

Arch:		any

Protects:	- hardware virtualization enable/disable

Comment:	'raw' because hardware enabling/disabling must be atomic /wrt

		migration.

virt/kvm/kvm_main.c

+10 −9
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ MODULE_LICENSE("GPL"); 
 */



DEFINE_RAW_SPINLOCK(kvm_lock);

static DEFINE_RAW_SPINLOCK(kvm_count_lock);

LIST_HEAD(vm_list);



static cpumask_var_t cpus_hardware_enabled;
@@ -2683,10 +2684,10 @@ static void hardware_enable_nolock(void *junk) 


static void hardware_enable(void)

{

	raw_spin_lock(&kvm_lock);

	raw_spin_lock(&kvm_count_lock);

	if (kvm_usage_count)

		hardware_enable_nolock(NULL);

	raw_spin_unlock(&kvm_lock);

	raw_spin_unlock(&kvm_count_lock);

}



static void hardware_disable_nolock(void *junk)
@@ -2701,10 +2702,10 @@ static void hardware_disable_nolock(void *junk) 


static void hardware_disable(void)

{

	raw_spin_lock(&kvm_lock);

	raw_spin_lock(&kvm_count_lock);

	if (kvm_usage_count)

		hardware_disable_nolock(NULL);

	raw_spin_unlock(&kvm_lock);

	raw_spin_unlock(&kvm_count_lock);

}



static void hardware_disable_all_nolock(void)
@@ -2718,16 +2719,16 @@ static void hardware_disable_all_nolock(void) 


static void hardware_disable_all(void)

{

	raw_spin_lock(&kvm_lock);

	raw_spin_lock(&kvm_count_lock);

	hardware_disable_all_nolock();

	raw_spin_unlock(&kvm_lock);

	raw_spin_unlock(&kvm_count_lock);

}



static int hardware_enable_all(void)

{

	int r = 0;



	raw_spin_lock(&kvm_lock);

	raw_spin_lock(&kvm_count_lock);



	kvm_usage_count++;

	if (kvm_usage_count == 1) {
@@ -2740,7 +2741,7 @@ static int hardware_enable_all(void) 
		}

	}



	raw_spin_unlock(&kvm_lock);

	raw_spin_unlock(&kvm_count_lock);



	return r;

}
@@ -3130,7 +3131,7 @@ static int kvm_suspend(void) 
static void kvm_resume(void)

{

	if (kvm_usage_count) {

		WARN_ON(raw_spin_is_locked(&kvm_lock));

		WARN_ON(raw_spin_is_locked(&kvm_count_lock));

		hardware_enable_nolock(NULL);

	}

}