This is a note to let you know that I've just added the patch titled arm64: Ignore any DMA offsets in the max_zone_phys() calculation to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: arm64-ignore-any-dma-offsets-in-the-max_zone_phys-calculation.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 791ab8b2e3db0c6e4295467d10398800ec29144c Mon Sep 17 00:00:00 2001 From: Catalin Marinas <catalin.marinas@xxxxxxx> Date: Wed, 18 Nov 2020 18:58:09 +0000 Subject: arm64: Ignore any DMA offsets in the max_zone_phys() calculation From: Catalin Marinas <catalin.marinas@xxxxxxx> commit 791ab8b2e3db0c6e4295467d10398800ec29144c upstream. Currently, the kernel assumes that if RAM starts above 32-bit (or zone_bits), there is still a ZONE_DMA/DMA32 at the bottom of the RAM and such constrained devices have a hardwired DMA offset. In practice, we haven't noticed any such hardware so let's assume that we can expand ZONE_DMA32 to the available memory if no RAM below 4GB. Similarly, ZONE_DMA is expanded to the 4GB limit if no RAM addressable by zone_bits. Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> Cc: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> Cc: Robin Murphy <robin.murphy@xxxxxxx> Link: https://lore.kernel.org/r/20201118185809.1078362-1-catalin.marinas@xxxxxxx Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/mm/init.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -174,14 +174,21 @@ static void __init reserve_elfcorehdr(vo #endif /* CONFIG_CRASH_DUMP */ /* - * Return the maximum physical address for a zone with a given address size - * limit. It currently assumes that for memory starting above 4G, 32-bit - * devices will use a DMA offset. + * Return the maximum physical address for a zone accessible by the given bits + * limit. If DRAM starts above 32-bit, expand the zone to the maximum + * available memory, otherwise cap it at 32-bit. */ static phys_addr_t __init max_zone_phys(unsigned int zone_bits) { - phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, zone_bits); - return min(offset + (1ULL << zone_bits), memblock_end_of_DRAM()); + phys_addr_t zone_mask = DMA_BIT_MASK(zone_bits); + phys_addr_t phys_start = memblock_start_of_DRAM(); + + if (phys_start > U32_MAX) + zone_mask = PHYS_ADDR_MAX; + else if (phys_start > zone_mask) + zone_mask = U32_MAX; + + return min(zone_mask, memblock_end_of_DRAM() - 1) + 1; } static void __init zone_sizes_init(unsigned long min, unsigned long max) Patches currently in stable-queue which might be from catalin.marinas@xxxxxxx are queue-5.10/arm64-force-no_block_mappings-if-crashkernel-reservation-is-required.patch queue-5.10/arm64-ignore-any-dma-offsets-in-the-max_zone_phys-calculation.patch