KVM: Convert kvm_lock back to non-raw spinlock

In commit e935b8372cf8 ("KVM: Convert kvm_lock to raw_spinlock"),
the kvm_lock was made a raw lock.  However, the kvm mmu_shrink()
function tries to grab the (non-raw) mmu_lock within the scope of
the raw locked kvm_lock being held.  This leads to the following:

BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 0, pid: 55, name: kswapd0
Preemption disabled at:[<ffffffffa0376eac>] mmu_shrink+0x5c/0x1b0 [kvm]

Pid: 55, comm: kswapd0 Not tainted 3.4.34_preempt-rt
Call Trace:
 [<ffffffff8106f2ad>] __might_sleep+0xfd/0x160
 [<ffffffff817d8d64>] rt_spin_lock+0x24/0x50
 [<ffffffffa0376f3c>] mmu_shrink+0xec/0x1b0 [kvm]
 [<ffffffff8111455d>] shrink_slab+0x17d/0x3a0
 [<ffffffff81151f00>] ? mem_cgroup_iter+0x130/0x260
 [<ffffffff8111824a>] balance_pgdat+0x54a/0x730
 [<ffffffff8111fe47>] ? set_pgdat_percpu_threshold+0xa7/0xd0
 [<ffffffff811185bf>] kswapd+0x18f/0x490
 [<ffffffff81070961>] ? get_parent_ip+0x11/0x50
 [<ffffffff81061970>] ? __init_waitqueue_head+0x50/0x50
 [<ffffffff81118430>] ? balance_pgdat+0x730/0x730
 [<ffffffff81060d2b>] kthread+0xdb/0xe0
 [<ffffffff8106e122>] ? finish_task_switch+0x52/0x100
 [<ffffffff817e1e94>] kernel_thread_helper+0x4/0x10
 [<ffffffff81060c50>] ? __init_kthread_worker+0x

After the previous patch, kvm_lock need not be a raw spinlock anymore,
so change it back.

Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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>

5 files changed, 17 insertions, 18 deletions

diff --git a/Documentation/virtual/kvm/locking.txt b/Documentation/virtual/kvm/locking.txt
index ba9e1c2150c2..f8869410d40c 100644
--- a/Documentation/virtual/kvm/locking.txt
+++ b/Documentation/virtual/kvm/locking.txt
@@ -132,7 +132,7 @@ See the comments in spte_has_volatile_bits() and mmu_spte_update().
 ------------
 
 Name:           kvm_lock
-Type:           raw_spinlock
+Type:           spinlock_t
 Arch:           any
 Protects:       - vm_list
 
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dce0df8150df..cf95cfe050a6 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4428,7 +4428,7 @@ mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
         int nr_to_scan = sc->nr_to_scan;
         unsigned long freed = 0;
 
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
 
         list_for_each_entry(kvm, &vm_list, vm_list) {
                 int idx;
@@ -4478,9 +4478,8 @@ unlock:
                 break;
         }
 
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
         return freed;
-
 }
 
 static unsigned long
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e5ca72a5cdb6..187f824b1454 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5263,7 +5263,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
 
         smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);
 
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_for_each_entry(kvm, &vm_list, vm_list) {
                 kvm_for_each_vcpu(i, vcpu, kvm) {
                         if (vcpu->cpu != freq->cpu)
@@ -5273,7 +5273,7 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
                                 send_ipi = 1;
                 }
         }
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
 
         if (freq->old < freq->new && send_ipi) {
                 /*
@@ -5426,12 +5426,12 @@ static void pvclock_gtod_update_fn(struct work_struct *work)
         struct kvm_vcpu *vcpu;
         int i;
 
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_for_each_entry(kvm, &vm_list, vm_list)
                 kvm_for_each_vcpu(i, vcpu, kvm)
                         set_bit(KVM_REQ_MASTERCLOCK_UPDATE, &vcpu->requests);
         atomic_set(&kvm_guest_has_master_clock, 0);
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
 }
 
 static DECLARE_WORK(pvclock_gtod_work, pvclock_gtod_update_fn);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 749bdb12cd15..7c961e1e9270 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -142,7 +142,7 @@ struct kvm;
 struct kvm_vcpu;
 extern struct kmem_cache *kvm_vcpu_cache;
 
-extern raw_spinlock_t kvm_lock;
+extern spinlock_t kvm_lock;
 extern struct list_head vm_list;
 
 struct kvm_io_range {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index eb94343c2ed2..d469114aff09 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -70,7 +70,7 @@ MODULE_LICENSE("GPL");
  *              kvm->lock --> kvm->slots_lock --> kvm->irq_lock
  */
 
-DEFINE_RAW_SPINLOCK(kvm_lock);
+DEFINE_SPINLOCK(kvm_lock);
 static DEFINE_RAW_SPINLOCK(kvm_count_lock);
 LIST_HEAD(vm_list);
 
@@ -491,9 +491,9 @@ static struct kvm *kvm_create_vm(unsigned long type)
         if (r)
                 goto out_err;
 
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_add(&kvm->vm_list, &vm_list);
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
 
         return kvm;
 
@@ -582,9 +582,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
         struct mm_struct *mm = kvm->mm;
 
         kvm_arch_sync_events(kvm);
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_del(&kvm->vm_list);
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
         kvm_free_irq_routing(kvm);
         for (i = 0; i < KVM_NR_BUSES; i++)
                 kvm_io_bus_destroy(kvm->buses[i]);
@@ -3054,10 +3054,10 @@ static int vm_stat_get(void *_offset, u64 *val)
         struct kvm *kvm;
 
         *val = 0;
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_for_each_entry(kvm, &vm_list, vm_list)
                 *val += *(u32 *)((void *)kvm + offset);
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
         return 0;
 }
 
@@ -3071,12 +3071,12 @@ static int vcpu_stat_get(void *_offset, u64 *val)
         int i;
 
         *val = 0;
-        raw_spin_lock(&kvm_lock);
+        spin_lock(&kvm_lock);
         list_for_each_entry(kvm, &vm_list, vm_list)
                 kvm_for_each_vcpu(i, vcpu, kvm)
                         *val += *(u32 *)((void *)vcpu + offset);
 
-        raw_spin_unlock(&kvm_lock);
+        spin_unlock(&kvm_lock);
         return 0;
 }