Re: [Xen-devel] [PATCH OSSTEST v5 00/13] support for ARM32 arndale and cubietruck platforms

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 23 Jan 2015, Ian Campbell wrote:
> On Thu, 2015-01-22 at 18:54 +0000, Stefano Stabellini wrote:
> > On Thu, 22 Jan 2015, Ian Campbell wrote:
> > > On Thu, 2015-01-22 at 10:56 +0000, Ian Campbell wrote:
> > > > I've managed to make a habit of forgetting to mention one important
> > > > point (including hitting send on this bit in reply to v4!)
> > > > 
> > > > Both the cubietruck and the arndale are (for different reasons) not
> > > > supported by the 3.14 kernel which we currently use as a baseline for
> > > > osstest testing.
> > > > 
> > > > I'm not sure if another LTS kernel is due from upstream soon or not, if
> > > > not then I think we will need to resurrect the linux-arm-xen branch and
> > > > use it for all arm platforms (including midway, since I don't think we
> > > > want to take on the complexity of differing per platform).
> > > > 
> > > > So far I've been testing using v3.16.7, which is the last 3.16 longterm
> > > > release, however canonical are carrying it on at
> > > > http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y
> > > > (up to 3.16.7-ckt4 at the moment). This is the same base as Debian will
> > > > be shipping in Jessie. So that is one option.
> > > > 
> > > > Stefano, do you have another preference?
> > > 
> > > We discussed this IRL and are going to resurrect the linux-arm-xen
> > > branch following the Canonical stable v3.16 branch.
> > > 
> > > Stefano,
> > > 
> > > Please could you pull from git://kernel.ubuntu.com/ubuntu/linux.git and
> > > the force push::
> > 
> > Actually I think we should follow
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git 
> > linux-3.16.y
> 
> There are no more updates to this, since it is not a kernel.org LTS
> kernel.
> 
> The canonical kernel team (ckt in the tag name) are doing ongoing stable
> support for these kernels (which is also being consumed by Debian).
> 
> > > The commit pointed to by tag v3.16.7-ckt4 (i.e. v3.16.7-ckt4~0) to the
> > 
> > I was talking about v3.16.7
> 
> This doesn't have e.g. the swiotlb/dma fixes which you have had
> backported, those are in the ckt kernels only.

You are right, I was mistaken.  However keep in mind that only the
ubuntu stable branch linux-3.16.y-queue has the following important
backport:

commit 342443e998bd2dd6406d46c5f7e62540a6d4a170
Author: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Date:   Fri Nov 21 11:07:39 2014 +0000

    xen/arm/arm64: introduce xen_arch_need_swiotlb
    
    commit a4dba130891271084344c12537731542ec77cb85 upstream.
    
    Introduce an arch specific function to find out whether a particular dma
    mapping operation needs to bounce on the swiotlb buffer.

the main linux-3.16.y branch (currently tagged v3.16.7-ckt4) doesn't have it 
yet.

Without it, DMA is not safe with non-coherent devices.

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