Re: [PATCH v4 0/7] Static shared memory followup v2 - pt2

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

+ Oleksii

> On 24 May 2024, at 13:40, Luca Fancellu <Luca.Fancellu@xxxxxxx> wrote:
> 
> This serie is a partial rework of this other serie:
> https://patchwork.kernel.org/project/xen-devel/cover/20231206090623.1932275-1-Penny.Zheng@xxxxxxx/
> 
> The original serie is addressing an issue of the static shared memory feature
> that impacts the memory footprint of other component when the feature is
> enabled, another issue impacts the device tree generation for the guests when
> the feature is enabled and used and the last one is a missing feature that is
> the option to have a static shared memory region that is not from the host
> address space.
> 
> This serie is handling some comment on the original serie and it is splitting
> the rework in two part, this first part is addressing the memory footprint 
> issue
> and the device tree generation and currently is fully merged
> (https://patchwork.kernel.org/project/xen-devel/cover/20240418073652.3622828-1-luca.fancellu@xxxxxxx/),
> this serie is addressing the static shared memory allocation from the Xen 
> heap.
> 
> Luca Fancellu (5):
>  xen/arm: Lookup bootinfo shm bank during the mapping
>  xen/arm: Wrap shared memory mapping code in one function
>  xen/arm: Parse xen,shared-mem when host phys address is not provided
>  xen/arm: Rework heap page allocation outside allocate_bank_memory
>  xen/arm: Implement the logic for static shared memory from Xen heap
> 
> Penny Zheng (2):
>  xen/p2m: put reference for level 2 superpage
>  xen/docs: Describe static shared memory when host address is not
>    provided
> 
> docs/misc/arm/device-tree/booting.txt   |  52 ++-
> xen/arch/arm/arm32/mmu/mm.c             |  11 +-
> xen/arch/arm/dom0less-build.c           |   4 +-
> xen/arch/arm/domain_build.c             |  84 +++--
> xen/arch/arm/include/asm/domain_build.h |   9 +-
> xen/arch/arm/mmu/p2m.c                  |  82 +++--
> xen/arch/arm/setup.c                    |  14 +-
> xen/arch/arm/static-shmem.c             | 432 +++++++++++++++++-------
> 8 files changed, 502 insertions(+), 186 deletions(-)
> 
> -- 
> 2.34.1
> 
> 

Hi,

We would like this serie to be in Xen 4.19, there was a misunderstanding on our 
side because we thought
that since the serie was sent before the last posting date, it could have been 
a candidate for merging in the
new release, instead after speaking with Julien and Oleksii we are now aware 
that we need to provide a
justification for its presence.

Pros to this serie is that we are closing the circle for static shared memory, 
allowing it to use memory from
the host or from Xen, it is also a feature that is not enabled by default, so 
it should not cause too much
disruption in case of any bugs that escaped the review, however we’ve tested 
many configurations for that
with/without enabling the feature if that can be an additional value.

Cons: we are touching some common code related to p2m, but also there the 
impact should be minimal because
the new code is subject to l2 foreign mapping (to be confirmed maybe from a p2m 
expert like Julien).

The comments on patch 3 of this serie are addressed by this patch:
https://patchwork.kernel.org/project/xen-devel/patch/20240528125603.2467640-1-luca.fancellu@xxxxxxx/
And the serie is fully reviewed.

So our request is to allow this serie in 4.19, Oleksii, ARM maintainers, do you 
agree on that?

Cheers,
Luca