6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yang Shi yang@os.amperecomputing.com
commit 56a708742a8bf127eb66798bfc9c9516c61f9930 upstream.
Commit ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by zone_dma_limit") and subsequent patches changed how zone_dma_limit is calculated to allow a reduced ZONE_DMA even when RAM starts above 4GB. Commit 122c234ef4e1 ("arm64: mm: keep low RAM dma zone") further fixed this to ensure ZONE_DMA remains below U32_MAX if RAM starts below 4GB, especially on platforms that do not have IORT or DT description of the device DMA ranges. While zone boundaries calculation was fixed by the latter commit, zone_dma_limit, used to determine the GFP_DMA flag in the core code, was not updated. This results in excessive use of GFP_DMA and unnecessary ZONE_DMA allocations on some platforms.
Update zone_dma_limit to match the actual upper bound of ZONE_DMA.
Fixes: ba0fb44aed47 ("dma-mapping: replace zone_dma_bits by zone_dma_limit") Cc: stable@vger.kernel.org # 6.12.x Reported-by: Yutang Jiang jiangyutang@os.amperecomputing.com Tested-by: Yutang Jiang jiangyutang@os.amperecomputing.com Signed-off-by: Yang Shi yang@os.amperecomputing.com Link: https://lore.kernel.org/r/20241125171650.77424-1-yang@os.amperecomputing.com [catalin.marinas@arm.com: some tweaking of the commit log] Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/mm/init.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-)
--- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -116,15 +116,6 @@ static void __init arch_reserve_crashker
static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit) { - /** - * Information we get from firmware (e.g. DT dma-ranges) describe DMA - * bus constraints. Devices using DMA might have their own limitations. - * Some of them rely on DMA zone in low 32-bit memory. Keep low RAM - * DMA zone on platforms that have RAM there. - */ - if (memblock_start_of_DRAM() < U32_MAX) - zone_limit = min(zone_limit, U32_MAX); - return min(zone_limit, memblock_end_of_DRAM() - 1) + 1; }
@@ -140,6 +131,14 @@ static void __init zone_sizes_init(void) acpi_zone_dma_limit = acpi_iort_dma_get_max_cpu_address(); dt_zone_dma_limit = of_dma_get_max_cpu_address(NULL); zone_dma_limit = min(dt_zone_dma_limit, acpi_zone_dma_limit); + /* + * Information we get from firmware (e.g. DT dma-ranges) describe DMA + * bus constraints. Devices using DMA might have their own limitations. + * Some of them rely on DMA zone in low 32-bit memory. Keep low RAM + * DMA zone on platforms that have RAM there. + */ + if (memblock_start_of_DRAM() < U32_MAX) + zone_dma_limit = min(zone_dma_limit, U32_MAX); arm64_dma_phys_limit = max_zone_phys(zone_dma_limit); max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); #endif