[PATCH] kvm: Convert kvm_lock to a mutex

From: Paolo Bonzini
Date: Tue Jun 04 2019 - 13:30:15 EST

From: Junaid Shahid <junaids@xxxxxxxxxx>

It doesn't seem as if there is any particular need for kvm_lock to be a
spinlock, so convert the lock to a mutex.

Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
Documentation/virtual/kvm/locking.txt | 4 +---
arch/s390/kvm/kvm-s390.c | 4 ++--
arch/x86/kvm/mmu.c | 4 ++--
arch/x86/kvm/x86.c | 14 +++++++-------
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 30 +++++++++++++++---------------
6 files changed, 28 insertions(+), 30 deletions(-)

diff --git a/Documentation/virtual/kvm/locking.txt b/Documentation/virtual/kvm/locking.txt
index 1bb8bcaf8497..635cd6eaf714 100644
--- a/Documentation/virtual/kvm/locking.txt
+++ b/Documentation/virtual/kvm/locking.txt
@@ -15,8 +15,6 @@ The acquisition orders for mutexes are as follows:

On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.

-For spinlocks, kvm_lock is taken outside kvm->mmu_lock.
-
Everything else is a leaf: no other lock is taken inside the critical
sections.

@@ -169,7 +167,7 @@ which time it will be set using the Dirty tracking mechanism described above.
------------

Name: kvm_lock
-Type: spinlock_t
+Type: mutex
Arch: any
Protects: - vm_list

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 7936af0a971f..0fef9192f6ac 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2423,13 +2423,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
kvm->arch.sca = (struct bsca_block *) get_zeroed_page(alloc_flags);
if (!kvm->arch.sca)
goto out_err;
- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
sca_offset += 16;
if (sca_offset + sizeof(struct bsca_block) > PAGE_SIZE)
sca_offset = 0;
kvm->arch.sca = (struct bsca_block *)
((char *) kvm->arch.sca + sca_offset);
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

sprintf(debug_name, "kvm-%u", current->pid);

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 95ac393e2959..3384c539d150 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5956,7 +5956,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
int nr_to_scan = sc->nr_to_scan;
unsigned long freed = 0;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);

list_for_each_entry(kvm, &vm_list, vm_list) {
int idx;
@@ -5998,7 +5998,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
break;
}

- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);
return freed;
}

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1ea651a6adea..d01e029faa31 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6719,7 +6719,7 @@ static void kvm_hyperv_tsc_notifier(void)
struct kvm_vcpu *vcpu;
int cpu;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list)
kvm_make_mclock_inprogress_request(kvm);

@@ -6745,7 +6745,7 @@ static void kvm_hyperv_tsc_notifier(void)

spin_unlock(&ka->pvclock_gtod_sync_lock);
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);
}
#endif

@@ -6796,17 +6796,17 @@ static void __kvmclock_cpufreq_notifier(struct cpufreq_freqs *freq, int cpu)

smp_call_function_single(cpu, tsc_khz_changed, freq, 1);

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
kvm_for_each_vcpu(i, vcpu, kvm) {
if (vcpu->cpu != cpu)
continue;
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
- if (vcpu->cpu != smp_processor_id())
+ if (vcpu->cpu != raw_smp_processor_id())
send_ipi = 1;
}
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

if (freq->old < freq->new && send_ipi) {
/*
@@ -6929,12 +6929,12 @@ static void pvclock_gtod_update_fn(struct work_struct *work)
struct kvm_vcpu *vcpu;
int i;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list)
kvm_for_each_vcpu(i, vcpu, kvm)
kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
atomic_set(&kvm_guest_has_master_clock, 0);
- spin_unlock(&kvm_lock);
+ mutex_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 5e9fd7ad8018..abafddb9fe2c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -162,7 +162,7 @@ static inline bool is_error_page(struct page *page)

extern struct kmem_cache *kvm_vcpu_cache;

-extern spinlock_t kvm_lock;
+extern struct mutex 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 b2579841263f..9613987ef4c8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -98,7 +98,7 @@
* kvm->lock --> kvm->slots_lock --> kvm->irq_lock
*/

-DEFINE_SPINLOCK(kvm_lock);
+DEFINE_MUTEX(kvm_lock);
static DEFINE_RAW_SPINLOCK(kvm_count_lock);
LIST_HEAD(vm_list);

@@ -683,9 +683,9 @@ static struct kvm *kvm_create_vm(unsigned long type)
if (r)
goto out_err;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_add(&kvm->vm_list, &vm_list);
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

preempt_notifier_inc();

@@ -731,9 +731,9 @@ static void kvm_destroy_vm(struct kvm *kvm)
kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
kvm_destroy_vm_debugfs(kvm);
kvm_arch_sync_events(kvm);
- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_del(&kvm->vm_list);
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);
kvm_free_irq_routing(kvm);
for (i = 0; i < KVM_NR_BUSES; i++) {
struct kvm_io_bus *bus = kvm_get_bus(kvm, i);
@@ -4034,13 +4034,13 @@ static int vm_stat_get(void *_offset, u64 *val)
u64 tmp_val;

*val = 0;
- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
stat_tmp.kvm = kvm;
vm_stat_get_per_vm((void *)&stat_tmp, &tmp_val);
*val += tmp_val;
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);
return 0;
}

@@ -4053,12 +4053,12 @@ static int vm_stat_clear(void *_offset, u64 val)
if (val)
return -EINVAL;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
stat_tmp.kvm = kvm;
vm_stat_clear_per_vm((void *)&stat_tmp, 0);
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

return 0;
}
@@ -4073,13 +4073,13 @@ static int vcpu_stat_get(void *_offset, u64 *val)
u64 tmp_val;

*val = 0;
- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
stat_tmp.kvm = kvm;
vcpu_stat_get_per_vm((void *)&stat_tmp, &tmp_val);
*val += tmp_val;
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);
return 0;
}

@@ -4092,12 +4092,12 @@ static int vcpu_stat_clear(void *_offset, u64 val)
if (val)
return -EINVAL;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list) {
stat_tmp.kvm = kvm;
vcpu_stat_clear_per_vm((void *)&stat_tmp, 0);
}
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

return 0;
}
@@ -4118,7 +4118,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
if (!kvm_dev.this_device || !kvm)
return;

- spin_lock(&kvm_lock);
+ mutex_lock(&kvm_lock);
if (type == KVM_EVENT_CREATE_VM) {
kvm_createvm_count++;
kvm_active_vms++;
@@ -4127,7 +4127,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
}
created = kvm_createvm_count;
active = kvm_active_vms;
- spin_unlock(&kvm_lock);
+ mutex_unlock(&kvm_lock);

env = kzalloc(sizeof(*env), GFP_KERNEL_ACCOUNT);
if (!env)
--
1.8.3.1