On Fri, Dec 22, 2023 at 07:35:52PM +0000, Alexander Graf wrote:
> When we finish populating our memory, we don't want to lose the scratch
> region as memory we can use for useful data. Do do that, we mark it as
> CMA memory. That means that any allocation within it only happens with
> movable memory which we can then happily discard for the next kexec.
>
> That way we don't lose the scratch region's memory anymore for
> allocations after boot.
>
> Signed-off-by: Alexander Graf <graf@xxxxxxxxxx>
>
> ---
>
> v1 -> v2:
>
> - test bot warning fix
> ---
> mm/memblock.c | 30 ++++++++++++++++++++++++++----
> 1 file changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e89e6c8f9d75..3700c2c1a96d 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -16,6 +16,7 @@
> #include <linux/kmemleak.h>
> #include <linux/seq_file.h>
> #include <linux/memblock.h>
> +#include <linux/page-isolation.h>
>
> #include <asm/sections.h>
> #include <linux/io.h>
> @@ -1100,10 +1101,6 @@ static bool should_skip_region(struct memblock_type *type,
> if ((flags & MEMBLOCK_SCRATCH) && !memblock_is_scratch(m))
> return true;
>
> - /* Leave scratch memory alone after scratch-only phase */
> - if (!(flags & MEMBLOCK_SCRATCH) && memblock_is_scratch(m))
> - return true;
> -
> return false;
> }
>
> @@ -2153,6 +2150,20 @@ static void __init __free_pages_memory(unsigned long start, unsigned long end)
> }
> }
>
> +#ifdef CONFIG_MEMBLOCK_SCRATCH
> +static void reserve_scratch_mem(phys_addr_t start, phys_addr_t end)
nit: the function name doesn't look reasonable as it has nothing
limiting it to neither reservation nor scratch mem.
Perhaps something like "set_mem_cma_type" would be a better fit.
> +{
> + ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
> + ulong end_pfn = pageblock_align(PFN_UP(end));
> + ulong pfn;
> +
> + for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
> + /* Mark as CMA to prevent kernel allocations in it */
nit: the comment above looks irrelevant/redundant.
> + set_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_CMA);
> + }
> +}
> +#endif
> +
> static unsigned long __init __free_memory_core(phys_addr_t start,
> phys_addr_t end)
> {
> @@ -2214,6 +2225,17 @@ static unsigned long __init free_low_memory_core_early(void)
>
> memmap_init_reserved_pages();
>
> +#ifdef CONFIG_MEMBLOCK_SCRATCH
> + /*
> + * Mark scratch mem as CMA before we return it. That way we ensure that
> + * no kernel allocations happen on it. That means we can reuse it as
> + * scratch memory again later.
> + */
> + __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
> + MEMBLOCK_SCRATCH, &start, &end, NULL)
> + reserve_scratch_mem(start, end);
> +#endif
> +
> /*
> * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
> * because in some case like Node0 doesn't have RAM installed
> --
> 2.40.1
>
>
>
>
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> Krausenstr. 38
> 10117 Berlin
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>
>
