KVM: introduce kvm_arch_vcpu_async_ioctl

After the vcpu_load/vcpu_put pushdown, the handling of asynchronous VCPU
ioctl is already much clearer in that it is obvious that they bypass
vcpu_load and vcpu_put.

However, it is still not perfect in that the different state of the VCPU
mutex is still hidden in the caller.  Separate those ioctls into a new
function kvm_arch_vcpu_async_ioctl that returns -ENOIOCTLCMD for more
"traditional" synchronous ioctls.

Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Suggested-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/Kconfig

@@ -22,6 +22,7 @@ config KVM
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
+	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select KVM_MMIO
 	select MMU_NOTIFIER
 	select SRCU

arch/mips/kvm/mips.c

@@ -903,12 +903,11 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 	return r;
 }
 
-long kvm_arch_vcpu_ioctl(struct file *filp, unsigned int ioctl,
+long kvm_arch_vcpu_async_ioctl(struct file *filp, unsigned int ioctl,
-			 unsigned long arg)
+			       unsigned long arg)
 {
 	struct kvm_vcpu *vcpu = filp->private_data;
 	void __user *argp = (void __user *)arg;
-	long r;
 
 	if (ioctl == KVM_INTERRUPT) {
 		struct kvm_mips_interrupt irq;
@@ -921,6 +920,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp, unsigned int ioctl,
 		return kvm_vcpu_ioctl_interrupt(vcpu, &irq);
 	}
 
+	return -ENOIOCTLCMD;
+}
+
+long kvm_arch_vcpu_ioctl(struct file *filp, unsigned int ioctl,
+			 unsigned long arg)
+{
+	struct kvm_vcpu *vcpu = filp->private_data;
+	void __user *argp = (void __user *)arg;
+	long r;
+
 	vcpu_load(vcpu);
 
 	switch (ioctl) {

arch/powerpc/kvm/Kconfig

@@ -22,6 +22,7 @@ config KVM
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
 	select HAVE_KVM_EVENTFD
+	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select SRCU
 	select KVM_VFIO
 	select IRQ_BYPASS_MANAGER

arch/powerpc/kvm/powerpc.c

@@ -1607,12 +1607,11 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 	return -EINVAL;
 }
 
-long kvm_arch_vcpu_ioctl(struct file *filp,
+long kvm_arch_vcpu_async_ioctl(struct file *filp,
-                         unsigned int ioctl, unsigned long arg)
+			       unsigned int ioctl, unsigned long arg)
 {
 	struct kvm_vcpu *vcpu = filp->private_data;
 	void __user *argp = (void __user *)arg;
-	long r;
 
 	if (ioctl == KVM_INTERRUPT) {
 		struct kvm_interrupt irq;
@@ -1620,6 +1619,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 			return -EFAULT;
 		return kvm_vcpu_ioctl_interrupt(vcpu, &irq);
 	}
+	return -ENOIOCTLCMD;
+}
+
+long kvm_arch_vcpu_ioctl(struct file *filp,
+                         unsigned int ioctl, unsigned long arg)
+{
+	struct kvm_vcpu *vcpu = filp->private_data;
+	void __user *argp = (void __user *)arg;
+	long r;
 
 	vcpu_load(vcpu);
 

arch/s390/kvm/Kconfig

@@ -23,6 +23,7 @@ config KVM
 	select PREEMPT_NOTIFIERS
 	select ANON_INODES
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
+	select HAVE_KVM_VCPU_ASYNC_IOCTL
 	select HAVE_KVM_EVENTFD
 	select KVM_ASYNC_PF
 	select KVM_ASYNC_PF_SYNC

arch/s390/kvm/kvm-s390.c

@@ -3725,13 +3725,11 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 	return r;
 }
 
-long kvm_arch_vcpu_ioctl(struct file *filp,
+long kvm_arch_vcpu_async_ioctl(struct file *filp,
-			 unsigned int ioctl, unsigned long arg)
+			       unsigned int ioctl, unsigned long arg)
 {
 	struct kvm_vcpu *vcpu = filp->private_data;
 	void __user *argp = (void __user *)arg;
-	int idx;
-	long r;
 
 	switch (ioctl) {
 	case KVM_S390_IRQ: {
@@ -3752,6 +3750,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		return kvm_s390_inject_vcpu(vcpu, &s390irq);
 	}
 	}
+	return -ENOIOCTLCMD;
+}
+
+long kvm_arch_vcpu_ioctl(struct file *filp,
+			 unsigned int ioctl, unsigned long arg)
+{
+	struct kvm_vcpu *vcpu = filp->private_data;
+	void __user *argp = (void __user *)arg;
+	int idx;
+	long r;
 
 	vcpu_load(vcpu);
 

include/linux/kvm_host.h

@@ -1260,4 +1260,16 @@ static inline bool vcpu_valid_wakeup(struct kvm_vcpu *vcpu)
 }
 #endif /* CONFIG_HAVE_KVM_INVALID_WAKEUPS */
 
+#ifdef CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL
+long kvm_arch_vcpu_async_ioctl(struct file *filp,
+			       unsigned int ioctl, unsigned long arg);
+#else
+static inline long kvm_arch_vcpu_async_ioctl(struct file *filp,
+					     unsigned int ioctl,
+					     unsigned long arg)
+{
+	return -ENOIOCTLCMD;
+}
+#endif /* CONFIG_HAVE_KVM_VCPU_ASYNC_IOCTL */
+
 #endif

virt/kvm/Kconfig

@@ -51,3 +51,6 @@ config KVM_COMPAT
 
 config HAVE_KVM_IRQ_BYPASS
        bool
+
+config HAVE_KVM_VCPU_ASYNC_IOCTL
+       bool

virt/kvm/kvm_main.c

@@ -2544,15 +2544,13 @@ static long kvm_vcpu_ioctl(struct file *filp,
 	if (unlikely(_IOC_TYPE(ioctl) != KVMIO))
 		return -EINVAL;
 
-#if defined(CONFIG_S390) || defined(CONFIG_PPC) || defined(CONFIG_MIPS)
 	/*
-	 * Special cases: vcpu ioctls that are asynchronous to vcpu execution,
+	 * Some architectures have vcpu ioctls that are asynchronous to vcpu
-	 * so vcpu_load() would break it.
+	 * execution; mutex_lock() would break them.
 	 */
-	if (ioctl == KVM_S390_INTERRUPT || ioctl == KVM_S390_IRQ || ioctl == KVM_INTERRUPT)
+	r = kvm_arch_vcpu_async_ioctl(filp, ioctl, arg);
-		return kvm_arch_vcpu_ioctl(filp, ioctl, arg);
+	if (r != -ENOIOCTLCMD)
-#endif
+		return r;
-
 
 	if (mutex_lock_killable(&vcpu->mutex))
 		return -EINTR;