[RFC PATCH 3/5] KVM: ARM VGIC add kvm_io_bus_ frontend

[n.nikolaev@virtualopensystems.com (Nikolay Nikolaev)]

In io_mem_abort remove the call to vgic_handle_mmio. The target is to have
a single MMIO handling path - that is through the kvm_io_bus_ API.

Register a kvm_io_device in kvm_vgic_init on the whole vGIC MMIO region.
Both read and write calls are redirected to vgic_io_dev_access where
kvm_exit_mmio is composed to pass it to vm_ops.handle_mmio.


Signed-off-by: Nikolay Nikolaev <n.nikolaev@virtualopensystems.com>
---
 arch/arm/kvm/mmio.c    |    3 --
 include/kvm/arm_vgic.h |    3 +-
 virt/kvm/arm/vgic.c    |   88 ++++++++++++++++++++++++++++++++++++++++--------
 3 files changed, 74 insertions(+), 20 deletions(-)

diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
index 81230da..1c44a2b 100644
--- a/arch/arm/kvm/mmio.c
+++ b/arch/arm/kvm/mmio.c
@@ -227,9 +227,6 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	if (mmio.is_write)
 		mmio_write_buf(mmio.data, mmio.len, data);
 
-	if (vgic_handle_mmio(vcpu, run, &mmio))
-		return 1;
-
 	if (handle_kernel_mmio(vcpu, run, &mmio))
 		return 1;
 
diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index e452ef7..d9b7d2a 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -233,6 +233,7 @@ struct vgic_dist {
 	unsigned long		*irq_pending_on_cpu;
 
 	struct vgic_vm_ops	vm_ops;
+	struct kvm_io_device	*io_dev;
 #endif
 };
 
@@ -307,8 +308,6 @@ int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
 			bool level);
 void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
 int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
-bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
-		      struct kvm_exit_mmio *mmio);
 
 #define irqchip_in_kernel(k)	(!!((k)->arch.vgic.in_kernel))
 #define vgic_initialized(k)	((k)->arch.vgic.ready)
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 1213da5..3da1115 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -31,6 +31,9 @@
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_mmu.h>
+#include <asm/kvm.h>
+
+#include "iodev.h"
 
 /*
  * How the whole thing works (courtesy of Christoffer Dall):
@@ -775,28 +778,81 @@ bool vgic_handle_mmio_range(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	return true;
 }
 
-/**
- * vgic_handle_mmio - handle an in-kernel MMIO access for the GIC emulation
- * @vcpu:      pointer to the vcpu performing the access
- * @run:       pointer to the kvm_run structure
- * @mmio:      pointer to the data describing the access
- *
- * returns true if the MMIO access has been performed in kernel space,
- * and false if it needs to be emulated in user space.
- * Calls the actual handling routine for the selected VGIC model.
- */
-bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
-		      struct kvm_exit_mmio *mmio)
+static int vgic_io_dev_access(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
+			    gpa_t addr, int len, void *val, bool is_write)
 {
-	if (!irqchip_in_kernel(vcpu->kvm))
-		return false;
+	struct kvm_exit_mmio mmio;
+	bool ret;
+
+	mmio = (struct kvm_exit_mmio) {
+		.phys_addr = addr,
+		.len = len,
+		.is_write = is_write,
+	};
+
+	if (is_write)
+		memcpy(mmio.data, val, len);
 
 	/*
 	 * This will currently call either vgic_v2_handle_mmio() or
 	 * vgic_v3_handle_mmio(), which in turn will call
 	 * vgic_handle_mmio_range() defined above.
 	 */
-	return vcpu->kvm->arch.vgic.vm_ops.handle_mmio(vcpu, run, mmio);
+	ret = vcpu->kvm->arch.vgic.vm_ops.handle_mmio(vcpu, vcpu->run, &mmio);
+
+	if (!is_write)
+		memcpy(val, mmio.data, len);
+
+	return ret ? 0 : 1;
+}
+
+static int vgic_io_dev_read(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
+			  gpa_t addr, int len, void *val)
+{
+	return vgic_io_dev_access(vcpu, this, addr, len, val, false);
+}
+
+static int vgic_io_dev_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
+			   gpa_t addr, int len, const void *val)
+{
+	return vgic_io_dev_access(vcpu, this, addr, len, (void *)val, true);
+}
+
+static const struct kvm_io_device_ops vgic_io_dev_ops = {
+	.read       = vgic_io_dev_read,
+	.write      = vgic_io_dev_write,
+};
+
+static int vgic_register_kvm_io_dev(struct kvm *kvm)
+{
+	struct kvm_io_device *dev;
+	int ret;
+
+	struct vgic_dist *dist = &kvm->arch.vgic;
+	unsigned long base = dist->vgic_dist_base;
+
+	dev = kzalloc(sizeof(struct kvm_io_device), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	kvm_iodevice_init(dev, &vgic_io_dev_ops);
+
+	mutex_lock(&kvm->slots_lock);
+
+	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS,
+			base, KVM_VGIC_V2_DIST_SIZE, dev);
+	if (ret < 0)
+		goto out_free_dev;
+	mutex_unlock(&kvm->slots_lock);
+
+	kvm->arch.vgic.io_dev = dev;
+
+	return 0;
+
+out_free_dev:
+	mutex_unlock(&kvm->slots_lock);
+	kfree(dev);
+	return ret;
 }
 
 static int vgic_nr_shared_irqs(struct vgic_dist *dist)
@@ -1545,6 +1601,8 @@ int kvm_vgic_init(struct kvm *kvm)
 
 	mutex_lock(&kvm->lock);
 
+	vgic_register_kvm_io_dev(kvm);
+
 	if (vgic_initialized(kvm))
 		goto out;