KVM: ARM: Introduce KVM_ARM_SET_DEVICE_ADDR ioctl

On ARM some bits are specific to the model being emulated for the guest and
user space needs a way to tell the kernel about those bits.  An example is mmio
device base addresses, where KVM must know the base address for a given device
to properly emulate mmio accesses within a certain address range or directly
map a device with virtualiation extensions into the guest address space.

We make this API ARM-specific as we haven't yet reached a consensus for a
generic API for all KVM architectures that will allow us to do something like
this.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 22 insertions, 1 deletions

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 2d30e3afdaf9..523f77a44e44 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -167,6 +167,8 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_COALESCED_MMIO:
                 r = KVM_COALESCED_MMIO_PAGE_OFFSET;
                 break;
+        case KVM_CAP_ARM_SET_DEVICE_ADDR:
+                r = 1;
         case KVM_CAP_NR_VCPUS:
                 r = num_online_cpus();
                 break;
@@ -827,10 +829,29 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct kvm_dirty_log *log)
         return -EINVAL;
 }
 
+static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
+                                        struct kvm_arm_device_addr *dev_addr)
+{
+        return -ENODEV;
+}
+
 long kvm_arch_vm_ioctl(struct file *filp,
                        unsigned int ioctl, unsigned long arg)
 {
-        return -EINVAL;
+        struct kvm *kvm = filp->private_data;
+        void __user *argp = (void __user *)arg;
+
+        switch (ioctl) {
+        case KVM_ARM_SET_DEVICE_ADDR: {
+                struct kvm_arm_device_addr dev_addr;
+
+                if (copy_from_user(&dev_addr, argp, sizeof(dev_addr)))
+                        return -EFAULT;
+                return kvm_vm_ioctl_set_device_addr(kvm, &dev_addr);
+        }
+        default:
+                return -EINVAL;
+        }
 }
 
 static void cpu_init_hyp_mode(void *vector)