[RFC PATCH v2 00/48] Make U-Boot memory reservations coherent

[Tom Rini]

On Thu, Jul 04, 2024 at 01:04:56PM +0530, Sughosh Ganu wrote:

> The aim of this patch series is to fix the current state of
> incoherence between modules when it comes to memory usage. The primary
> issue that this series is trying to fix is that the EFI memory module
> which is responsible for allocating and freeing memory, does not have
> any visibility of the memory that is being used by the LMB
> module. This is further complicated by the fact that the LMB
> allocations are caller specific -- the LMB memory map is not global
> nor persistent. This means that the memory "allocated" by the LMB
> module might be relevant only for a given function. Hence one of the
> requirements for making the memory usage visible across modules is to
> make LMB allocations persistent and global, and then have means to
> communicate the use of memory across modules.
> 
> The first set of patches in this series work on making the LMB memory
> map persistent and global. This is being done keeping in mind the
> usage of LMB memory by platforms where the same memory region can be
> used to load multiple different images. What is not allowed is to
> overwrite memory that has been allocated by the other module,
> currently the EFI memory module. This is being achieved by introducing
> a new flag, LMB_NOOVERWRITE, which represents memory which cannot be
> re-requested once allocated.
> 
> A review comment on the earlier version was to do away with the static
> arrays for the LMB lists of free and used memory. This version
> uses the alloced list data structure for the LMB lists.
> 
> The second set of patches are making changes to the EFI memory module
> to make use of the LMB functions to allocate and free memory. A
> *_flags() version of LMB API's has been introduced for the same. The
> earlier version was using notification mechanism from both LMB and EFI
> modules to maintain memory coherence. This version makes use of the
> LMB API functions for the memory allocations. This is based on review
> comments of EFI maintainers.

Please re-work so that the series is bisectable. For example
xilinx_zynqmp_r5 fails that check currently. And I found that looking in
to why it grows by ~1500 bytes overall. This likely is due to
CONFIG_EFI_LOADER=n and so while the case where EFI_LOADER is enabled
tends to be a size win (reduction) or wash we need to look at the
CONFIG_EFI_LOADER=n case more. The alist code will be a little growth
and that's fine enough. But realloc and do_bdinfo are the two big
growths at the top, in this case.

-- 
Tom
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