On IO memory abort, try to handle the MMIO access thorugh the KVM
registered read/write callbacks. This is done by invoking the relevant
kvm_io_bus_* API.

Signed-off-by: Nikolay Nikolaev <redacted>
---
 arch/arm/kvm/mmio.c |   33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
index 4cb5a93..81230da 100644
--- a/arch/arm/kvm/mmio.c
+++ b/arch/arm/kvm/mmio.c

@@ -162,6 +162,36 @@ static int decode_hsr(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	return 0;
 }
 
+/**
+ * kvm_handle_mmio - handle an in-kernel MMIO access
+ * @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.
+ */
+static bool handle_kernel_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
+		struct kvm_exit_mmio *mmio)
+{
+	int ret;
+
+	if (mmio->is_write) {
+		ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
+				mmio->len, &mmio->data);
+
+	} else {
+		ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
+				mmio->len, &mmio->data);
+	}
+	if (!ret) {
+		kvm_prepare_mmio(run, mmio);
+		kvm_handle_mmio_return(vcpu, run);
+	}
+
+	return !ret;
+}
+
 int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		 phys_addr_t fault_ipa)
 {

@@ -200,6 +230,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	if (vgic_handle_mmio(vcpu, run, &mmio))
 		return 1;
 
+	if (handle_kernel_mmio(vcpu, run, &mmio))
+		return 1;
+