| Message ID | 20201118185809.1078362-1-catalin.marinas@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: Ignore any DMA offsets in the max_zone_phys() calculation | expand |
On Wed, 2020-11-18 at 18:58 +0000, Catalin Marinas wrote: > 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@arm.com> > Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > Cc: Robin Murphy <robin.murphy@arm.com> > --- Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> On RPi4 and QEMU: Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Regards, Nicolas
On Wed, 18 Nov 2020 18:58:09 +0000, Catalin Marinas wrote: > 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. Applied to arm64 (for-next/zone-dma-default-32-bit), thanks for the review/test! [1/1] arm64: Ignore any DMA offsets in the max_zone_phys() calculation https://git.kernel.org/arm64/c/791ab8b2e3db
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 1ab1e8313500..4807b4a54222 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -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)
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@arm.com> Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Cc: Robin Murphy <robin.murphy@arm.com> --- arch/arm64/mm/init.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)