From 1a65b73ae9abd608575e9bfbaa003d829d39fab9 Mon Sep 17 00:00:00 2001 From: Sumanth Korikkar Date: Mon, 8 Jan 2024 14:27:44 +0100 Subject: s390/mm: allocate vmemmap pages from self-contained memory range Allocate memory map (struct pages array) from the hotplugged memory range, rather than using system memory. The change addresses the issue where standby memory, when configured to be much larger than online memory, could potentially lead to ipl failure due to memory map allocation from online memory. For example, 16MB of memory map allocation is needed for a memory block size of 1GB and when standby memory is configured much larger than online memory, this could lead to ipl failure. To address this issue, the solution involves introducing "memmap on memory" using the vmem_altmap structure on s390. Architectures that want to implement it should pass the altmap to the vmemmap_populate() function and its associated callchain. This enhancement is discussed in commit 4b94ffdc4163 ("x86, mm: introduce vmem_altmap to augment vmemmap_populate()") Provide "memmap on memory" support for s390 by passing the altmap in vmemmap_populate() and its callchain. The allocation path is described as follows: * When altmap is NULL in vmemmap_populate(), memory map allocation occurs using the existing vmemmap_alloc_block_buf(). * When altmap is not NULL in vmemmap_populate(), memory map allocation still uses vmemmap_alloc_block_buf(), but this function internally calls altmap_alloc_block_buf(). For deallocation, the process is outlined as follows: * When altmap is NULL in vmemmap_free(), memory map deallocation happens through free_pages(). * When altmap is not NULL in vmemmap_free(), memory map deallocation occurs via vmem_altmap_free(). While memory map allocation is primarily handled through the self-contained memory map range, there might still be a small amount of system memory allocation required for vmemmap pagetables. To mitigate this impact, this feature will be limited to machines with EDAT1 support. Link: https://lkml.kernel.org/r/20240108132747.3238763-3-sumanthk@linux.ibm.com Reviewed-by: Gerald Schaefer Signed-off-by: Sumanth Korikkar Cc: Alexander Gordeev Cc: Aneesh Kumar K.V Cc: Anshuman Khandual Cc: David Hildenbrand Cc: Heiko Carstens Cc: Michal Hocko Cc: Oscar Salvador Cc: Vasily Gorbik Signed-off-by: Andrew Morton --- arch/s390/mm/init.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch/s390/mm/init.c') diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c index 43e612bc2bcd..8d9a60ccb777 100644 --- a/arch/s390/mm/init.c +++ b/arch/s390/mm/init.c @@ -281,9 +281,6 @@ int arch_add_memory(int nid, u64 start, u64 size, unsigned long size_pages = PFN_DOWN(size); int rc; - if (WARN_ON_ONCE(params->altmap)) - return -EINVAL; - if (WARN_ON_ONCE(params->pgprot.pgprot != PAGE_KERNEL.pgprot)) return -EINVAL; -- cgit v1.2.3