drm/amdkfd: don't allow mapping the MMIO HDP page with large pages

commit be4a2a8 upstream.

We don't get the right offset in that case.  The GPU has
an unused 4K area of the register BAR space into which you can
remap registers.  We remap the HDP flush registers into this
space to allow userspace (CPU or GPU) to flush the HDP when it
updates VRAM.  However, on systems with >4K pages, we end up
exposing PAGE_SIZE of MMIO space.

Fixes: d8e408a ("drm/amdkfd: Expose HDP registers to user space")
Reviewed-by: Felix Kuehling <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Cc: [email protected]
Signed-off-by: Felix Kuehling <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

drivers/gpu/drm/amd/amdkfd/kfd_chardev.c

@@ -1290,7 +1290,7 @@ static int kfd_ioctl_alloc_memory_of_gpu(struct file *filep,
 			goto err_unlock;
 		}
 		offset = amdgpu_amdkfd_get_mmio_remap_phys_addr(dev->kgd);
-		if (!offset) {
+		if (!offset || (PAGE_SIZE > 4096)) {
 			err = -ENOMEM;
 			goto err_unlock;
 		}
@@ -2029,6 +2029,9 @@ static int kfd_mmio_mmap(struct kfd_dev *dev, struct kfd_process *process,
 	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
 		return -EINVAL;
 
+	if (PAGE_SIZE > 4096)
+		return -EINVAL;
+
 	address = amdgpu_amdkfd_get_mmio_remap_phys_addr(dev->kgd);
 
 	vma->vm_flags |= VM_IO | VM_DONTCOPY | VM_DONTEXPAND | VM_NORESERVE |