Re: [PATCH v2] mm: disable kernelcore=mirror when no mirror memory

[Mike Rapoport <rppt@kernel.org>]

On Wed, Aug 02, 2023 at 03:23:28PM +0800, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> For system with kernelcore=mirror enabled while no mirrored memory is
> reported by efi. This could lead to kernel OOM during startup since
> all memory beside zone DMA are in the movable zone and this prevents
> the kernel to use it.
> 
> Zone DMA/DMA32 initialization is independent of mirrored memory and
> their max pfn is set in zone_sizes_init(). Since kernel can fallback
> to zone DMA/DMA32 if there is no memory in zone Normal, these zones
> are seen as mirrored memory no mather their memory attributes are.
> 
> To solve this problem, disable kernelcore=mirror when there is no real
> mirrored memory exists.
> 
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Suggested-by: Mike Rapoport <rppt@kernel.org>
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>

Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  mm/internal.h | 1 +
>  mm/memblock.c | 5 +++++
>  mm/mm_init.c  | 5 +++++
>  3 files changed, 11 insertions(+)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index a7d9e980429a..b8aaf9cac87e 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1005,6 +1005,7 @@ static inline bool gup_must_unshare(struct vm_area_struct *vma,
>  }
>  
>  extern bool mirrored_kernelcore;
> +extern bool memblock_has_mirror(void);
>  
>  static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
>  {
> diff --git a/mm/memblock.c b/mm/memblock.c
> index f9e61e565a53..913b2520a9a0 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -161,6 +161,11 @@ static int memblock_can_resize __initdata_memblock;
>  static int memblock_memory_in_slab __initdata_memblock;
>  static int memblock_reserved_in_slab __initdata_memblock;
>  
> +bool __init_memblock memblock_has_mirror(void)
> +{
> +	return system_has_some_mirror;
> +}
> +
>  static enum memblock_flags __init_memblock choose_memblock_flags(void)
>  {
>  	return system_has_some_mirror ? MEMBLOCK_MIRROR : MEMBLOCK_NONE;
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index a1963c3322af..e8af1b628430 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -377,6 +377,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>  	if (mirrored_kernelcore) {
>  		bool mem_below_4gb_not_mirrored = false;
>  
> +		if (!memblock_has_mirror()) {
> +			pr_warn("The system has no mirror memory, ignore kernelcore=mirror.\n");
> +			goto out;
> +		}
> +
>  		for_each_mem_region(r) {
>  			if (memblock_is_mirror(r))
>  				continue;
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.