Re: [BACKPORT] swiotlb-xen: implement xen_swiotlb_dma_mmap callback

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Sep 14, 2017 at 04:23:05PM -0700, Stefano Stabellini wrote:
> Hi all,
> 
> We are getting reports from Xen on ARM users about DMA issues. The
> problem is that the commit below
> (7e91c7df29b5e196de3dc6f086c8937973bd0b88) is necessary to support mmap
> on Xen on ARM. It is self-contained and doesn't affect anything outside
> of Xen on ARM, so I think is a good candidate for backporting. It went
> upstream in 4.11.

But it's a new feature, right?  How does that fit the stable kernel
rules?

> 
> 
> Could you please backport the following commit:
> 
>   commit 7e91c7df29b5e196de3dc6f086c8937973bd0b88
>   Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>   Date:   Tue Feb 7 19:58:02 2017 +0200
>   
>       swiotlb-xen: implement xen_swiotlb_dma_mmap callback
>       
>       This function creates userspace mapping for the DMA-coherent memory.
>     
> to the stable trees up until 3.14?
> 
> 
> Because of 00085f1efa387a8ce100e3734920f7639c80caa3 "dma-mapping: use
> unsigned long for dma_attrs", the appended patch (to be applied on top)
> is required for trees older than 4.8. 

What does the kvm maintainers think about this?

thanks,

greg k-h