KVM: s390: Lock kvm->srcu at the appropriate places

The kvm->srcu lock has to be held while accessing the memory of
guests and during certain other actions. This patch now adds
the locks to the __vcpu_run function so that all affected code
is protected now (and additionally to the KVM_S390_STORE_STATUS
ioctl, which can be called out-of-band and needs a separate lock).

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 16 insertions, 3 deletions

diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 3a74d8af0d69..78d967f180f4 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -107,14 +107,13 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
 
 static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
 {
-        int ret, idx;
+        int ret;
 
         /* No virtio-ccw notification? Get out quickly. */
         if (!vcpu->kvm->arch.css_support ||
             (vcpu->run->s.regs.gprs[1] != KVM_S390_VIRTIO_CCW_NOTIFY))
                 return -EOPNOTSUPP;
 
-        idx = srcu_read_lock(&vcpu->kvm->srcu);
         /*
          * The layout is as follows:
          * - gpr 2 contains the subchannel id (passed as addr)
@@ -125,7 +124,6 @@ static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
                                       vcpu->run->s.regs.gprs[2],
                                       8, &vcpu->run->s.regs.gprs[3],
                                       vcpu->run->s.regs.gprs[4]);
-        srcu_read_unlock(&vcpu->kvm->srcu, idx);
 
         /*
          * Return cookie in gpr 2, but don't overwrite the register if the
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index 7f35cb33e510..e7323cd9f109 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -436,6 +436,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
         hrtimer_start(&vcpu->arch.ckc_timer, ktime_set (0, sltime) , HRTIMER_MODE_REL);
         VCPU_EVENT(vcpu, 5, "enabled wait via clock comparator: %llx ns", sltime);
 no_timer:
+        srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
         spin_lock(&vcpu->arch.local_int.float_int->lock);
         spin_lock_bh(&vcpu->arch.local_int.lock);
         add_wait_queue(&vcpu->wq, &wait);
@@ -455,6 +456,8 @@ no_timer:
         remove_wait_queue(&vcpu->wq, &wait);
         spin_unlock_bh(&vcpu->arch.local_int.lock);
         spin_unlock(&vcpu->arch.local_int.float_int->lock);
+        vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+
         hrtimer_try_to_cancel(&vcpu->arch.ckc_timer);
         return 0;
 }
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 8eec7abc5664..1e4e7b97337a 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -752,11 +752,18 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
 {
         int rc, exit_reason;
 
+        /*
+         * We try to hold kvm->srcu during most of vcpu_run (except when run-
+         * ning the guest), so that memslots (and other stuff) are protected
+         */
+        vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+
         do {
                 rc = vcpu_pre_run(vcpu);
                 if (rc)
                         break;
 
+                srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
                 /*
                  * As PF_VCPU will be used in fault handler, between
                  * guest_enter and guest_exit should be no uaccess.
@@ -767,10 +774,12 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
                 exit_reason = sie64a(vcpu->arch.sie_block,
                                      vcpu->run->s.regs.gprs);
                 kvm_guest_exit();
+                vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
 
                 rc = vcpu_post_run(vcpu, exit_reason);
         } while (!signal_pending(current) && !rc);
 
+        srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
         return rc;
 }
 
@@ -968,6 +977,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 {
         struct kvm_vcpu *vcpu = filp->private_data;
         void __user *argp = (void __user *)arg;
+        int idx;
         long r;
 
         switch (ioctl) {
@@ -981,7 +991,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
                 break;
         }
         case KVM_S390_STORE_STATUS:
+                idx = srcu_read_lock(&vcpu->kvm->srcu);
                 r = kvm_s390_vcpu_store_status(vcpu, arg);
+                srcu_read_unlock(&vcpu->kvm->srcu, idx);
                 break;
         case KVM_S390_SET_INITIAL_PSW: {
                 psw_t psw;