[RFC PATCH 1/2] kexec: do not place the next kernel in a fixed-address CMA area

[sashiko-bot at kernel.org]

> kexec_alloc_contig() picks the destination of the next kernel out of the
> default CMA area, and the next kernel then runs from there in place
> instead of being copied out. That is only safe if the area will not exist
> at the same address in the kernel being loaded.
> 
> For an area whose base came from the device tree, it will. The loaded
> kernel parses the same description, declares the range it is executing
> from as a shared-dma-pool, and cma_activate_area() releases the pages
> holding its own image to the page allocator.
> 
> Distinguish the two cases. An area placed by cma_declare_contiguous_nid()
> without a fixed base lands wherever this kernel found room, and the next
> kernel repeats that search against its own memblock state, so it cannot
> collide. Record the difference as CMA_FIXED_BASE and refuse to use such
> an area for the payload, which leaves kexec_locate_mem_hole() to fall
> [ ... ]
> them overlapping the running kernel.
> 
> Fixes: 07d24902977e ("kexec: enable CMA based contiguous allocation")
> Assisted-by: Claude:claude-opus-5
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey at amd.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261014145731.3431527-1-radhey.shyam.pandey@amd.com?part=1