KVM: s390: implement KVM_(S|G)ET_MP_STATE for user space state control

This patch
- adds s390 specific MP states to linux headers and documents them
- implements the KVM_{SET,GET}_MP_STATE ioctls
- enables KVM_CAP_MP_STATE
- allows user space to control the VCPU state on s390.

If user space sets the VCPU state using the ioctl KVM_SET_MP_STATE, we can disable
manual changing of the VCPU state and trust user space to do the right thing.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

5 files changed, 44 insertions, 6 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 4181d7baabba..c2ba0208a0e1 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -418,6 +418,7 @@ struct kvm_arch{
         int css_support;
         int use_irqchip;
         int use_cmma;
+        int user_cpu_state_ctrl;
         struct s390_io_adapter *adapters[MAX_S390_IO_ADAPTERS];
         wait_queue_head_t ipte_wq;
         spinlock_t start_stop_lock;
diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
index 0161675878a2..59bd8f991b98 100644
--- a/arch/s390/kvm/diag.c
+++ b/arch/s390/kvm/diag.c
@@ -176,7 +176,8 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
                 return -EOPNOTSUPP;
         }
 
-        kvm_s390_vcpu_stop(vcpu);
+        if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
+                kvm_s390_vcpu_stop(vcpu);
         vcpu->run->s390_reset_flags |= KVM_S390_RESET_SUBSYSTEM;
         vcpu->run->s390_reset_flags |= KVM_S390_RESET_IPL;
         vcpu->run->s390_reset_flags |= KVM_S390_RESET_CPU_INIT;
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index ac6b32585a36..eaf46291d361 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -73,7 +73,8 @@ static int handle_stop(struct kvm_vcpu *vcpu)
                         return rc;
         }
 
-        kvm_s390_vcpu_stop(vcpu);
+        if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
+                kvm_s390_vcpu_stop(vcpu);
         return -EOPNOTSUPP;
 }
 
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 342895350825..fdf88f7a539c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -167,6 +167,7 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_DEVICE_CTRL:
         case KVM_CAP_ENABLE_CAP_VM:
         case KVM_CAP_VM_ATTRIBUTES:
+        case KVM_CAP_MP_STATE:
                 r = 1;
                 break;
         case KVM_CAP_NR_VCPUS:
@@ -595,7 +596,8 @@ static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu)
         vcpu->arch.sie_block->pp = 0;
         vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
         kvm_clear_async_pf_completion_queue(vcpu);
-        kvm_s390_vcpu_stop(vcpu);
+        if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
+                kvm_s390_vcpu_stop(vcpu);
         kvm_s390_clear_local_irqs(vcpu);
 }
 
@@ -980,13 +982,34 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
                                     struct kvm_mp_state *mp_state)
 {
-        return -EINVAL; /* not implemented yet */
+        /* CHECK_STOP and LOAD are not supported yet */
+        return is_vcpu_stopped(vcpu) ? KVM_MP_STATE_STOPPED :
+                                       KVM_MP_STATE_OPERATING;
 }
 
 int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
                                     struct kvm_mp_state *mp_state)
 {
-        return -EINVAL; /* not implemented yet */
+        int rc = 0;
+
+        /* user space knows about this interface - let it control the state */
+        vcpu->kvm->arch.user_cpu_state_ctrl = 1;
+
+        switch (mp_state->mp_state) {
+        case KVM_MP_STATE_STOPPED:
+                kvm_s390_vcpu_stop(vcpu);
+                break;
+        case KVM_MP_STATE_OPERATING:
+                kvm_s390_vcpu_start(vcpu);
+                break;
+        case KVM_MP_STATE_LOAD:
+        case KVM_MP_STATE_CHECK_STOP:
+                /* fall through - CHECK_STOP and LOAD are not supported yet */
+        default:
+                rc = -ENXIO;
+        }
+
+        return rc;
 }
 
 bool kvm_s390_cmma_enabled(struct kvm *kvm)
@@ -1284,7 +1307,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         if (vcpu->sigset_active)
                 sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
 
-        kvm_s390_vcpu_start(vcpu);
+        if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm)) {
+                kvm_s390_vcpu_start(vcpu);
+        } else if (is_vcpu_stopped(vcpu)) {
+                pr_err_ratelimited("kvm-s390: can't run stopped vcpu %d\n",
+                                   vcpu->vcpu_id);
+                return -EINVAL;
+        }
 
         switch (kvm_run->exit_reason) {
         case KVM_EXIT_S390_SIEIC:
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 77ed846342d4..33a0e4bed2a5 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -129,6 +129,12 @@ static inline void kvm_s390_set_psw_cc(struct kvm_vcpu *vcpu, unsigned long cc)
         vcpu->arch.sie_block->gpsw.mask |= cc << 44;
 }
 
+/* are cpu states controlled by user space */
+static inline int kvm_s390_user_cpu_state_ctrl(struct kvm *kvm)
+{
+        return kvm->arch.user_cpu_state_ctrl != 0;
+}
+
 int kvm_s390_handle_wait(struct kvm_vcpu *vcpu);
 enum hrtimer_restart kvm_s390_idle_wakeup(struct hrtimer *timer);
 void kvm_s390_tasklet(unsigned long parm);