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KVM: protect kvm_usage_count with its own spinlock

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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: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-09-10 12:58:35 +02:00
parent 4fa92fb25a
commit 4a937f96f3
2 changed files with 15 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
Documentation/virtual/kvm/locking.txt
View File

@ -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.

19
virt/kvm/kvm_main.c
View File

@ -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);
}
}