[PATCH 4.9 18/31] kvm: Convert kvm_lock to a mutex

Greg Kroah-Hartman
2019-11-15T06:22:19Z

From: Junaid Shahid <junaids@google.com>

commit 0d9ce162cf46c99628cc5da9510b959c7976735b upstream.

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 so that sleepable functions (in
particular cond_resched()) can be called while holding it.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 4.9:
- Drop changes in kvm_hyperv_tsc_notifier(), vm_stat_clear(),
vcpu_stat_clear(), kvm_uevent_notify_change()
- Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/virtual/kvm/locking.txt | 6 +++---
arch/s390/kvm/kvm-s390.c | 4 ++--
arch/x86/kvm/mmu.c | 4 ++--
arch/x86/kvm/x86.c | 10 +++++-----
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 18 +++++++++---------
6 files changed, 22 insertions(+), 22 deletions(-)

--- a/Documentation/virtual/kvm/locking.txt
+++ b/Documentation/virtual/kvm/locking.txt
@@ -13,8 +13,8 @@ The acquisition orders for mutexes are a
- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring
them together is quite rare.

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

2: Exception
------------
@@ -142,7 +142,7 @@ See the comments in spte_has_volatile_bi
------------

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

--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1422,13 +1422,13 @@ int kvm_arch_init_vm(struct kvm *kvm, un
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);

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4979,7 +4979,7 @@ mmu_shrink_scan(struct shrinker *shrink,
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;
@@ -5029,7 +5029,7 @@ unlock:
break;
}

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

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5978,17 +5978,17 @@ static int kvmclock_cpufreq_notifier(str

smp_call_function_single(freq->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 != freq->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) {
/*
@@ -6126,12 +6126,12 @@ static void pvclock_gtod_update_fn(struc
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);
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -129,7 +129,7 @@ static inline bool is_error_page(struct

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 {
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -87,7 +87,7 @@ module_param(halt_poll_ns_shrink, uint,
* 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);

@@ -666,9 +666,9 @@ static struct kvm *kvm_create_vm(unsigne
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();

@@ -724,9 +724,9 @@ static void kvm_destroy_vm(struct kvm *k

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++) {
if (kvm->buses[i])
@@ -3752,13 +3752,13 @@ static int vm_stat_get(void *_offset, u6
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;
}

@@ -3772,13 +3772,13 @@ static int vcpu_stat_get(void *_offset,
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;
}