[PATCH v5 6/9] KVM: s390: Fix locking in kvm_s390_set_mem_control()

[Claudio Imbrenda]

All subfunctions in kvm_s390_set_mem_control() need to take the
kvm->lock, so factor it out of the switch.

Also add the missing locking around dat_reset_cmma().

Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
---
 arch/s390/kvm/kvm-s390.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ffb20a64d328..93141a68e0dd 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -962,6 +962,8 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 {
 	int ret;
 
+	guard(mutex)(&kvm->lock);
+
 	switch (attr->attr) {
 	case KVM_S390_VM_MEM_ENABLE_CMMA:
 		ret = -ENXIO;
@@ -969,7 +971,6 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 			break;
 
 		VM_EVENT(kvm, 3, "%s", "ENABLE: CMMA support");
-		mutex_lock(&kvm->lock);
 		if (kvm->created_vcpus)
 			ret = -EBUSY;
 		else {
@@ -978,7 +979,6 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 			kvm->arch.use_pfmfi = 0;
 			ret = 0;
 		}
-		mutex_unlock(&kvm->lock);
 		break;
 	case KVM_S390_VM_MEM_CLR_CMMA: {
 		gfn_t start_gfn = 0;
@@ -992,7 +992,8 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 
 		VM_EVENT(kvm, 3, "%s", "RESET: CMMA states");
 		do {
-			start_gfn = dat_reset_cmma(kvm->arch.gmap->asce, start_gfn);
+			scoped_guard(read_lock, &kvm->mmu_lock)
+				start_gfn = dat_reset_cmma(kvm->arch.gmap->asce, start_gfn);
 			cond_resched();
 		} while (start_gfn);
 		ret = 0;
@@ -1010,8 +1011,6 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
 		if (get_user(new_limit, (u64 __user *)attr->addr))
 			return -EFAULT;
 
-		guard(mutex)(&kvm->lock);
-
 		new_limit = ALIGN(new_limit, HPAGE_SIZE);
 		if (kvm->arch.mem_limit != KVM_S390_NO_MEM_LIMIT &&
 		    new_limit > kvm->arch.mem_limit)
-- 
2.54.0