KVM: PPC: Book3S: Add API for in-kernel XICS emulation

This adds the API for userspace to instantiate an XICS device in a VM
and connect VCPUs to it. The API consists of a new device type for
the KVM_CREATE_DEVICE ioctl, a new capability KVM_CAP_IRQ_XICS, which
functions similarly to KVM_CAP_IRQ_MPIC, and the KVM_IRQ_LINE ioctl,
which is used to assert and deassert interrupt inputs of the XICS.

The XICS device has one attribute group, KVM_DEV_XICS_GRP_SOURCES.
Each attribute within this group corresponds to the state of one
interrupt source. The attribute number is the same as the interrupt
source number.

This does not support irq routing or irqfd yet.

Signed-off-by: Paul Mackerras <[e-mail]>
Acked-by: David Gibson <[e-mail]>
Signed-off-by: Alexander Graf <[e-mail]>

Documentation/virtual/kvm/api.txt

···
             args[1] is the MPIC CPU number for this vcpu
 
 This capability connects the vcpu to an in-kernel MPIC device.
+
+6.7 KVM_CAP_IRQ_XICS
+
+Architectures: ppc
+Parameters: args[0] is the XICS device fd
+            args[1] is the XICS CPU number (server ID) for this vcpu
+
+This capability connects the vcpu to an in-kernel XICS device.

Documentation/virtual/kvm/devices/xics.txt

···
+XICS interrupt controller
+
+Device type supported: KVM_DEV_TYPE_XICS
+
+Groups:
+  KVM_DEV_XICS_SOURCES
+  Attributes: One per interrupt source, indexed by the source number.
+
+This device emulates the XICS (eXternal Interrupt Controller
+Specification) defined in PAPR.  The XICS has a set of interrupt
+sources, each identified by a 20-bit source number, and a set of
+Interrupt Control Presentation (ICP) entities, also called "servers",
+each associated with a virtual CPU.
+
+The ICP entities are created by enabling the KVM_CAP_IRQ_ARCH
+capability for each vcpu, specifying KVM_CAP_IRQ_XICS in args[0] and
+the interrupt server number (i.e. the vcpu number from the XICS's
+point of view) in args[1] of the kvm_enable_cap struct.  Each ICP has
+64 bits of state which can be read and written using the
+KVM_GET_ONE_REG and KVM_SET_ONE_REG ioctls on the vcpu.  The 64 bit
+state word has the following bitfields, starting at the
+least-significant end of the word:
+
+* Unused, 16 bits
+
+* Pending interrupt priority, 8 bits
+  Zero is the highest priority, 255 means no interrupt is pending.
+
+* Pending IPI (inter-processor interrupt) priority, 8 bits
+  Zero is the highest priority, 255 means no IPI is pending.
+
+* Pending interrupt source number, 24 bits
+  Zero means no interrupt pending, 2 means an IPI is pending
+
+* Current processor priority, 8 bits
+  Zero is the highest priority, meaning no interrupts can be
+  delivered, and 255 is the lowest priority.
+
+Each source has 64 bits of state that can be read and written using
+the KVM_GET_DEVICE_ATTR and KVM_SET_DEVICE_ATTR ioctls, specifying the
+KVM_DEV_XICS_SOURCES attribute group, with the attribute number being
+the interrupt source number.  The 64 bit state word has the following
+bitfields, starting from the least-significant end of the word:
+
+* Destination (server number), 32 bits
+  This specifies where the interrupt should be sent, and is the
+  interrupt server number specified for the destination vcpu.
+
+* Priority, 8 bits
+  This is the priority specified for this interrupt source, where 0 is
+  the highest priority and 255 is the lowest.  An interrupt with a
+  priority of 255 will never be delivered.
+
+* Level sensitive flag, 1 bit
+  This bit is 1 for a level-sensitive interrupt source, or 0 for
+  edge-sensitive (or MSI).
+
+* Masked flag, 1 bit
+  This bit is set to 1 if the interrupt is masked (cannot be delivered
+  regardless of its priority), for example by the ibm,int-off RTAS
+  call, or 0 if it is not masked.
+
+* Pending flag, 1 bit
+  This bit is 1 if the source has a pending interrupt, otherwise 0.
+
+Only one XICS instance may be created per VM.

arch/powerpc/include/asm/kvm_ppc.h

···
 extern int kvmppc_xics_hcall(struct kvm_vcpu *vcpu, u32 cmd);
 extern u64 kvmppc_xics_get_icp(struct kvm_vcpu *vcpu);
 extern int kvmppc_xics_set_icp(struct kvm_vcpu *vcpu, u64 icpval);
+extern int kvmppc_xics_connect_vcpu(struct kvm_device *dev,
+			struct kvm_vcpu *vcpu, u32 cpu);
 #else
 static inline int kvmppc_xics_enabled(struct kvm_vcpu *vcpu)
 	{ return 0; }

arch/powerpc/include/uapi/asm/kvm.h

···
 #define KVM_REG_PPC_TLB3PS	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x9a)
 #define KVM_REG_PPC_EPTCFG	(KVM_REG_PPC | KVM_REG_SIZE_U32 | 0x9b)
 
+/* PPC64 eXternal Interrupt Controller Specification */
+#define KVM_DEV_XICS_GRP_SOURCES	1	/* 64-bit source attributes */
+
+/* Layout of 64-bit source attribute values */
+#define  KVM_XICS_DESTINATION_SHIFT	0
+#define  KVM_XICS_DESTINATION_MASK	0xffffffffULL
+#define  KVM_XICS_PRIORITY_SHIFT	32
+#define  KVM_XICS_PRIORITY_MASK		0xff
+#define  KVM_XICS_LEVEL_SENSITIVE	(1ULL << 40)
+#define  KVM_XICS_MASKED		(1ULL << 41)
+#define  KVM_XICS_PENDING		(1ULL << 42)
+
 #endif /* __LINUX_KVM_POWERPC_H */

arch/powerpc/kvm/book3s_xics.c

···
 #include <linux/kvm_host.h>
 #include <linux/err.h>
 #include <linux/gfp.h>
+#include <linux/anon_inodes.h>
 
 #include <asm/uaccess.h>
 #include <asm/kvm_book3s.h>
···
  *
  * - Make ICS lockless as well, or at least a per-interrupt lock or hashed
  *   locks array to improve scalability
- *
- * - ioctl's to save/restore the entire state for snapshot & migration
  */
 
 /* -- ICS routines -- */
···
 static void icp_deliver_irq(struct kvmppc_xics *xics, struct kvmppc_icp *icp,
 			    u32 new_irq);
 
-static int ics_deliver_irq(struct kvmppc_xics *xics, u32 irq, u32 level)
+static int ics_deliver_irq(struct kvmppc_xics *xics, u32 irq, u32 level,
+			   bool report_status)
 {
 	struct ics_irq_state *state;
 	struct kvmppc_ics *ics;
···
 	if (!state->exists)
 		return -EINVAL;
 
+	if (report_status)
+		return state->asserted;
+
 	/*
 	 * We set state->asserted locklessly. This should be fine as
 	 * we are the only setter, thus concurrent access is undefined
···
 	/* Attempt delivery */
 	icp_deliver_irq(xics, NULL, irq);
 
-	return 0;
+	return state->asserted;
 }
 
 static void ics_check_resend(struct kvmppc_xics *xics, struct kvmppc_ics *ics,
···
 	kfree(name);
 }
 
-struct kvmppc_ics *kvmppc_xics_create_ics(struct kvm *kvm,
-					  struct kvmppc_xics *xics, int irq)
+static struct kvmppc_ics *kvmppc_xics_create_ics(struct kvm *kvm,
+					struct kvmppc_xics *xics, int irq)
 {
 	struct kvmppc_ics *ics;
 	int i, icsid;
···
 	return 0;
 }
 
-/* -- ioctls -- */
-
-int kvm_vm_ioctl_xics_irq(struct kvm *kvm, struct kvm_irq_level *args)
+static int xics_get_source(struct kvmppc_xics *xics, long irq, u64 addr)
 {
-	struct kvmppc_xics *xics;
-	int r;
+	int ret;
+	struct kvmppc_ics *ics;
+	struct ics_irq_state *irqp;
+	u64 __user *ubufp = (u64 __user *) addr;
+	u16 idx;
+	u64 val, prio;
 
-	/* locking against multiple callers? */
+	ics = kvmppc_xics_find_ics(xics, irq, &idx);
+	if (!ics)
+		return -ENOENT;
 
-	xics = kvm->arch.xics;
-	if (!xics)
-		return -ENODEV;
-
-	switch (args->level) {
-	case KVM_INTERRUPT_SET:
-	case KVM_INTERRUPT_SET_LEVEL:
-	case KVM_INTERRUPT_UNSET:
-		r = ics_deliver_irq(xics, args->irq, args->level);
-		break;
-	default:
-		r = -EINVAL;
+	irqp = &ics->irq_state[idx];
+	mutex_lock(&ics->lock);
+	ret = -ENOENT;
+	if (irqp->exists) {
+		val = irqp->server;
+		prio = irqp->priority;
+		if (prio == MASKED) {
+			val |= KVM_XICS_MASKED;
+			prio = irqp->saved_priority;
+		}
+		val |= prio << KVM_XICS_PRIORITY_SHIFT;
+		if (irqp->asserted)
+			val |= KVM_XICS_LEVEL_SENSITIVE | KVM_XICS_PENDING;
+		else if (irqp->masked_pending || irqp->resend)
+			val |= KVM_XICS_PENDING;
+		ret = 0;
 	}
+	mutex_unlock(&ics->lock);
 
-	return r;
+	if (!ret && put_user(val, ubufp))
+		ret = -EFAULT;
+
+	return ret;
 }
 
-void kvmppc_xics_free(struct kvmppc_xics *xics)
+static int xics_set_source(struct kvmppc_xics *xics, long irq, u64 addr)
 {
+	struct kvmppc_ics *ics;
+	struct ics_irq_state *irqp;
+	u64 __user *ubufp = (u64 __user *) addr;
+	u16 idx;
+	u64 val;
+	u8 prio;
+	u32 server;
+
+	if (irq < KVMPPC_XICS_FIRST_IRQ || irq >= KVMPPC_XICS_NR_IRQS)
+		return -ENOENT;
+
+	ics = kvmppc_xics_find_ics(xics, irq, &idx);
+	if (!ics) {
+		ics = kvmppc_xics_create_ics(xics->kvm, xics, irq);
+		if (!ics)
+			return -ENOMEM;
+	}
+	irqp = &ics->irq_state[idx];
+	if (get_user(val, ubufp))
+		return -EFAULT;
+
+	server = val & KVM_XICS_DESTINATION_MASK;
+	prio = val >> KVM_XICS_PRIORITY_SHIFT;
+	if (prio != MASKED &&
+	    kvmppc_xics_find_server(xics->kvm, server) == NULL)
+		return -EINVAL;
+
+	mutex_lock(&ics->lock);
+	irqp->server = server;
+	irqp->saved_priority = prio;
+	if (val & KVM_XICS_MASKED)
+		prio = MASKED;
+	irqp->priority = prio;
+	irqp->resend = 0;
+	irqp->masked_pending = 0;
+	irqp->asserted = 0;
+	if ((val & KVM_XICS_PENDING) && (val & KVM_XICS_LEVEL_SENSITIVE))
+		irqp->asserted = 1;
+	irqp->exists = 1;
+	mutex_unlock(&ics->lock);
+
+	if (val & KVM_XICS_PENDING)
+		icp_deliver_irq(xics, NULL, irqp->number);
+
+	return 0;
+}
+
+int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level,
+		bool line_status)
+{
+	struct kvmppc_xics *xics = kvm->arch.xics;
+
+	return ics_deliver_irq(xics, irq, level, line_status);
+}
+
+static int xics_set_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	struct kvmppc_xics *xics = dev->private;
+
+	switch (attr->group) {
+	case KVM_DEV_XICS_GRP_SOURCES:
+		return xics_set_source(xics, attr->attr, attr->addr);
+	}
+	return -ENXIO;
+}
+
+static int xics_get_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	struct kvmppc_xics *xics = dev->private;
+
+	switch (attr->group) {
+	case KVM_DEV_XICS_GRP_SOURCES:
+		return xics_get_source(xics, attr->attr, attr->addr);
+	}
+	return -ENXIO;
+}
+
+static int xics_has_attr(struct kvm_device *dev, struct kvm_device_attr *attr)
+{
+	switch (attr->group) {
+	case KVM_DEV_XICS_GRP_SOURCES:
+		if (attr->attr >= KVMPPC_XICS_FIRST_IRQ &&
+		    attr->attr < KVMPPC_XICS_NR_IRQS)
+			return 0;
+		break;
+	}
+	return -ENXIO;
+}
+
+static void kvmppc_xics_free(struct kvm_device *dev)
+{
+	struct kvmppc_xics *xics = dev->private;
 	int i;
 	struct kvm *kvm = xics->kvm;
 
···
 	for (i = 0; i <= xics->max_icsid; i++)
 		kfree(xics->ics[i]);
 	kfree(xics);
+	kfree(dev);
 }
 
-int kvm_xics_create(struct kvm *kvm, u32 type)
+static int kvmppc_xics_create(struct kvm_device *dev, u32 type)
 {
 	struct kvmppc_xics *xics;
+	struct kvm *kvm = dev->kvm;
 	int ret = 0;
 
 	xics = kzalloc(sizeof(*xics), GFP_KERNEL);
 	if (!xics)
 		return -ENOMEM;
 
+	dev->private = xics;
+	xics->dev = dev;
 	xics->kvm = kvm;
 
 	/* Already there ? */
···
 #endif /* CONFIG_KVM_BOOK3S_64_HV */
 
 	return 0;
+}
+
+struct kvm_device_ops kvm_xics_ops = {
+	.name = "kvm-xics",
+	.create = kvmppc_xics_create,
+	.destroy = kvmppc_xics_free,
+	.set_attr = xics_set_attr,
+	.get_attr = xics_get_attr,
+	.has_attr = xics_has_attr,
+};
+
+int kvmppc_xics_connect_vcpu(struct kvm_device *dev, struct kvm_vcpu *vcpu,
+			     u32 xcpu)
+{
+	struct kvmppc_xics *xics = dev->private;
+	int r = -EBUSY;
+
+	if (dev->ops != &kvm_xics_ops)
+		return -EPERM;
+	if (xics->kvm != vcpu->kvm)
+		return -EPERM;
+	if (vcpu->arch.irq_type)
+		return -EBUSY;
+
+	r = kvmppc_xics_create_icp(vcpu, xcpu);
+	if (!r)
+		vcpu->arch.irq_type = KVMPPC_IRQ_XICS;
+
+	return r;
 }
 
 void kvmppc_xics_free_icp(struct kvm_vcpu *vcpu)

arch/powerpc/kvm/book3s_xics.h

···
 
 struct kvmppc_xics {
 	struct kvm *kvm;
+	struct kvm_device *dev;
 	struct dentry *dentry;
 	u32 max_icsid;
 	bool real_mode;

arch/powerpc/kvm/irq.h

···
 #ifdef CONFIG_KVM_MPIC
 	ret = ret || (kvm->arch.mpic != NULL);
 #endif
+#ifdef CONFIG_KVM_XICS
+	ret = ret || (kvm->arch.xics != NULL);
+#endif
 	smp_rmb();
 	return ret;
 }

arch/powerpc/kvm/powerpc.c

···
 	case KVM_CAP_SPAPR_TCE:
 	case KVM_CAP_PPC_ALLOC_HTAB:
 	case KVM_CAP_PPC_RTAS:
+#ifdef CONFIG_KVM_XICS
+	case KVM_CAP_IRQ_XICS:
+#endif
 		r = 1;
 		break;
 #endif /* CONFIG_PPC_BOOK3S_64 */
···
 		break;
 	}
 #endif
+#ifdef CONFIG_KVM_XICS
+	case KVM_CAP_IRQ_XICS: {
+		struct file *filp;
+		struct kvm_device *dev;
+
+		r = -EBADF;
+		filp = fget(cap->args[0]);
+		if (!filp)
+			break;
+
+		r = -EPERM;
+		dev = kvm_device_from_filp(filp);
+		if (dev)
+			r = kvmppc_xics_connect_vcpu(dev, vcpu, cap->args[1]);
+
+		fput(filp);
+		break;
+	}
+#endif /* CONFIG_KVM_XICS */
 	default:
 		r = -EINVAL;
 		break;

include/linux/kvm_host.h

···
 struct kvm_device *kvm_device_from_filp(struct file *filp);
 
 extern struct kvm_device_ops kvm_mpic_ops;
+extern struct kvm_device_ops kvm_xics_ops;
 
 #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
 

include/uapi/linux/kvm.h

···
 #define KVM_CAP_DEVICE_CTRL 89
 #define KVM_CAP_IRQ_MPIC 90
 #define KVM_CAP_PPC_RTAS 91
+#define KVM_CAP_IRQ_XICS 92
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
···
 
 #define KVM_DEV_TYPE_FSL_MPIC_20	1
 #define KVM_DEV_TYPE_FSL_MPIC_42	2
+#define KVM_DEV_TYPE_XICS		3
 
 /*
  * ioctls for VM fds

virt/kvm/kvm_main.c

···
 		ops = &kvm_mpic_ops;
 		break;
 #endif
+#ifdef CONFIG_KVM_XICS
+	case KVM_DEV_TYPE_XICS:
+		ops = &kvm_xics_ops;
+		break;
+#endif
 	default:
 		return -ENODEV;
 	}