Re: [Xen-devel] [RFC PATCH 00/19] xen/arm: Add ITS support

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 9 Mar 2015, Vijay Kilari wrote:
> On Tue, Mar 3, 2015 at 5:13 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> > Hello Vijay,
> >
> > On 03/03/2015 03:55, Vijay Kilari wrote:
> >>
> >> On Mon, Mar 2, 2015 at 6:49 PM, Julien Grall <julien.grall@xxxxxxxxxx>
> >> wrote:
> >>>
> >>> On 02/03/15 12:30, vijay.kilari@xxxxxxxxx wrote:
> >>>>
> >>>> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> >>>>
> >>>> Add ITS support for arm. Following major features
> >>>> are supported
> >>>>   - GICv3 ITS support for arm64 platform
> >>>>   - Supports only single ITS node
> >>>
> >>>
> >>> Why only one ITS node supported? I though Cavium was using 2 ITS...
> >>
> >>
> >> I will update for 2 ITS nodes later when NUMA is supported
> >
> >
> > Why do you speak about NUMA? AFAICT, there is no requirement to support NUMA
> > for having multiple ITS...
> >
> > With multiple ITS support, your vITS emulation will likely heavily change.
> > So it would be nice to have this support as soon as possible.
> 
> Incremental changes (as separate patch series)
> would be more meaningful. I will have a look at it
> and if possible I will incorporate in next series
> 
> >
> >>>
> >>>>   - LPI descriptors are allocated on-demand
> >>>>   - Only ITS Dom0 is supported
> >>>
> >>>
> >>> Any plan to support guest?
> >>
> >>
> >> Yes, I will do it in next version
> >
> >
> > What is missing to support guest? Only the toolstack part?
> 
> Yes, it is only toolstack part similar to GICv3
> 
> >
> >>>
> >>>> Vijaya Kumar K (19):
> >>>>    xen/arm: add linked list apis
> >>>>    xen/arm: its: Import GICv3 ITS driver from linux
> >>>>    xen/arm: its: Port ITS driver to xen
> >>>
> >>>
> >>> A general comment (I haven't read closely the patches). The GICv3 ITS
> >>> taken from Linux is modified so heavily (rename function, move out code,
> >>> dropping unused code...) that your assumption in patch #1 [1] is wrong.
> >>>
> >>> At the end of this series it would make impossible to backport patch
> >>> from Linux.
> >>
> >>
> >>    Most of the code is reused or moved to different file based on Xen
> >> requirement.
> >>      - code like msi registered callback (setup_irq & teardown_irq) is of
> >> no use in Xen. So removed
> >>      - irq_chip is different in linux
> >>      - some of the functions like encode of ITS commands can be used in
> >> virtual ITS
> >>        driver as well. So have to be moved out to header file
> >>      - the LPI allocation is moved to virtual ITS driver. We can
> >> consider it keeping in physical ITS
> >>        driver but it fits well in virtual ITS driver rather than
> >> physical ITS driver.
> >
> >
> > IHMO, moving the code around two files make the code more difficult to
> > review because the patch is bigger.
> >
> > That also means we can't really review the first couple of patches because
> > the code will change a lot after.
> >
> > But the maintainers may be disagree with me...
> >
> >>>
> >>> Regards,
> >>>
> >>> [1] "This is actual GICv3 ITS driver from Linux. [..] This helps to
> >>> import any issues found in Linux"
> >>
> >>
> >> I have kept the linux GICv3 ITS driver in first patch and made incremental
> >> changes just to have better understanding and incremental approach
> >
> >
> > But this is doesn't help to backport issue from Linux...
> >
> > BTW, do you have a tree with all the code?
> 
> Yes, I have a tree, But I cannot share it. Github is ok?

Github is fine.

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