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Shutemov" , Mahesh J Salgaonkar , Michael Ellerman , Madhavan Srinivasan , "Aneesh Kumar K . V" , Donet Tom , LKML , "Ritesh Harjani (IBM)" , Sachin P Bappalige Subject: [RFC 1/2] cma: Fix CMA_MIN_ALIGNMENT_BYTES during early_init Date: Tue, 8 Oct 2024 18:57:18 +0530 Message-ID: X-Mailer: git-send-email 2.46.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit During early init CMA_MIN_ALIGNMENT_BYTES can be PAGE_SIZE, since pageblock_order is still zero and it gets initialized later during paging_init() e.g. paging_init() -> free_area_init() -> set_pageblock_order(). One such use case is - early_setup() -> early_init_devtree() -> fadump_reserve_mem() This causes CMA memory alignment check to be bypassed in cma_init_reserved_mem(). Then later cma_activate_area() can hit a VM_BUG_ON_PAGE(pfn & ((1 << order) - 1)) if the reserved memory area was not pageblock_order aligned. Instead of fixing it locally for fadump case on PowerPC, I believe this should be fixed for CMA_MIN_ALIGNMENT_BYTES. ============== page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10010 flags: 0x13ffff800000000(node=1|zone=0|lastcpupid=0x7ffff) CMA raw: 013ffff800000000 5deadbeef0000100 5deadbeef0000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: VM_BUG_ON_PAGE(pfn & ((1 << order) - 1)) ------------[ cut here ]------------ kernel BUG at mm/page_alloc.c:778! Call Trace: __free_one_page+0x57c/0x7b0 (unreliable) free_pcppages_bulk+0x1a8/0x2c8 free_unref_page_commit+0x3d4/0x4e4 free_unref_page+0x458/0x6d0 init_cma_reserved_pageblock+0x114/0x198 cma_init_reserved_areas+0x270/0x3e0 do_one_initcall+0x80/0x2f8 kernel_init_freeable+0x33c/0x530 kernel_init+0x34/0x26c ret_from_kernel_user_thread+0x14/0x1c Reported-by: Sachin P Bappalige Signed-off-by: Ritesh Harjani (IBM) --- include/linux/cma.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/cma.h b/include/linux/cma.h index 9db877506ea8..20abc6561bcd 100644 --- a/include/linux/cma.h +++ b/include/linux/cma.h @@ -5,6 +5,7 @@ #include #include #include +#include #ifdef CONFIG_CMA_AREAS #define MAX_CMA_AREAS CONFIG_CMA_AREAS @@ -17,7 +18,8 @@ * -- can deal with only some pageblocks of a higher-order page being * MIGRATE_CMA, we can use pageblock_nr_pages. */ -#define CMA_MIN_ALIGNMENT_PAGES pageblock_nr_pages +#define CMA_MIN_ALIGNMENT_PAGES \ + (1ULL << min_not_zero(MAX_PAGE_ORDER, pageblock_order)) #define CMA_MIN_ALIGNMENT_BYTES (PAGE_SIZE * CMA_MIN_ALIGNMENT_PAGES) struct cma; -- 2.46.0