Commit 791ab8b2 authored by Catalin Marinas's avatar Catalin Marinas
Browse files

arm64: Ignore any DMA offsets in the max_zone_phys() calculation 



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: default avatarCatalin Marinas <catalin.marinas@arm.com>
Tested-by: default avatarNicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: default avatarNicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Cc: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20201118185809.1078362-1-catalin.marinas@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent f8394f23

arch/arm64/mm/init.c

+12 −5
Original line number Diff line number Diff line
@@ -175,14 +175,21 @@ static void __init reserve_elfcorehdr(void) 
#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)