Re: [PATCH 5/5] virtio: Add bounce DMA ops

[Stefano Stabellini]

On Tue, 28 Apr 2020, Srivatsa Vaddagiri wrote:
> For better security, its desirable that a guest VM's memory is
> not accessible to any entity that executes outside the context of
> guest VM. In case of virtio, backend drivers execute outside the
> context of guest VM and in general will need access to complete
> guest VM memory.  One option to restrict the access provided to
> backend driver is to make use of a bounce buffer. The bounce
> buffer is accessible to both backend and frontend drivers. All IO
> buffers that are in private space of guest VM are bounced to be
> accessible to backend.

[...]

> +static int __init virtio_bounce_setup(struct reserved_mem *rmem)
> +{
> +	unsigned long node = rmem->fdt_node;
> +
> +	if (!of_get_flat_dt_prop(node, "no-map", NULL))
> +		return -EINVAL;
> +
> +	return virtio_register_bounce_buffer(rmem->base, rmem->size);
> +}
> +
> +RESERVEDMEM_OF_DECLARE(virtio, "virtio_bounce_pool", virtio_bounce_setup);

Is this special reserved-memory region documented somewhere?