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: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 4a937f96f3a29c58b7edd349d2e4dfac371efdf2)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/Documentation/virtual/kvm/locking.txt b/Documentation/virtual/kvm/locking.txt
index 41b7ac9884b5ebdeaba602077bebb11efebcc648..b1f5de22d090619527f80c9017197553bcc9d1e5 100644 (file)
--- a/Documentation/virtual/kvm/locking.txt
+++ b/Documentation/virtual/kvm/locking.txt
@@ -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.
 

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7103b989ba54a4749102b300e97a3a62ad8b61df..6bc0481bf8e51ad7fb3fc13a903d027849ef1ada 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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;
 }
@@ -3050,7 +3051,7 @@ 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);
        }
 }