[PATCH 2/3] KVM: protect kvm_usage_count with its own spinlock

[Paolo Bonzini]

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

Cc: sta...@vger.kernel.org
Cc: kvm@vger.kernel.org
Cc: g...@redhat.com
Cc: jan.kis...@siemens.com
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 Documentation/virtual/kvm/locking.txt |  6 +++++-
 virt/kvm/kvm_main.c                   | 19 ++++++++++---------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/Documentation/virtual/kvm/locking.txt 
b/Documentation/virtual/kvm/locking.txt
index a9f366e..ba9e1c2 100644
--- 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 75522b3..da13379 100644
--- 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;
 }
@@ -3133,7 +3134,7 @@ 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);
        }
 }
-- 
1.8.3.1


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