> On Oct 21, 2019, at 10:34 AM, Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> wrote: > > On Mon, 2019-10-21 at 10:15 -0400, Qian Cai wrote: >>> On Sep 11, 2019, at 2:25 PM, Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> >>> wrote: >>> >>> So far all arm64 devices have supported 32 bit DMA masks for their >>> peripherals. This is not true anymore for the Raspberry Pi 4 as most of >>> it's peripherals can only address the first GB of memory on a total of >>> up to 4 GB. >>> >>> This goes against ZONE_DMA32's intent, as it's expected for ZONE_DMA32 >>> to be addressable with a 32 bit mask. So it was decided to re-introduce >>> ZONE_DMA in arm64. >>> >>> ZONE_DMA will contain the lower 1G of memory, which is currently the >>> memory area addressable by any peripheral on an arm64 device. >>> ZONE_DMA32 will contain the rest of the 32 bit addressable memory. >>> >>> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx> >>> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> >>> >>> --- >> >> With ZONE_DMA=y, this config will fail to reserve 512M CMA on a server, >> >> https://raw.githubusercontent.com/cailca/linux-mm/master/arm64.config >> >> CONFIG_DMA_CMA=y >> CONFIG_CMA_SIZE_MBYTES=64 >> CONFIG_CMA_SIZE_SEL_MBYTES=y >> CONFIG_CMA_ALIGNMENT=8 >> CONFIG_CMA=y >> CONFIG_CMA_DEBUGFS=y >> CONFIG_CMA_AREAS=7 >> >> Is this expected? > > Not really, just tested cma=512M on a Raspberry Pi4, and it went well. The only > thing on my build that differs from your config is CONFIG_CMA_DEBUGFS. > > Could you post more information on the device you're experiencing this on? Also > some logs. With the above config, it does not even need "cma=512M" kernel cmdline. [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x431f0af1] [ 0.000000] Linux version 5.4.0-rc4-next-20191021+ (clang version 8.0.1 (Red Hat 8.0.1-1.module+el8.1.0+3866+6be7f4d8)) #1 SMP Mon Oct 21 10:03:03 EDT 2019 [ 0.000000] Setting debug_guardpage_minorder to 1 [ 0.000000] efi: Getting EFI parameters from FDT: [ 0.000000] efi: EFI v2.70 by American Megatrends [ 0.000000] efi: ESRT=0xf935ed98 SMBIOS=0xfcc90000 SMBIOS 3.0=0xfcc80000 ACPI 2.0=0xfac80000 MEMRESERVE=0xfacd1018 [ 0.000000] esrt: Reserving ESRT space from 0x00000000f935ed98 to 0x00000000f935edd0. [ 0.000000] crashkernel reserved: 0x00000097db400000 - 0x00000097fb400000 (512 MB) [ 0.000000] cma: Reserved 512 MiB at 0x00000000a0000000 With ZONE_DMA=y, it will say, cma: Failed to reserve 512 MiB The machine is a ThunderX2 server. https://buy.hpe.com/us/en/servers/apollo-systems/apollo-70-system/apollo-70-system/hpe-apollo-70-system/p/1010742472 # lscpu Architecture: aarch64 Byte Order: Little Endian CPU(s): 256 On-line CPU(s) list: 0-255 Thread(s) per core: 4 Core(s) per socket: 32 Socket(s): 2 NUMA node(s): 2 Vendor ID: Cavium Model: 1 Model name: ThunderX2 99xx Stepping: 0x1 BogoMIPS: 400.00 L1d cache: 32K L1i cache: 32K L2 cache: 256K L3 cache: 32768K NUMA node0 CPU(s): 0-127 NUMA node1 CPU(s): 128-255 Flags: fp asimd aes pmull sha1 sha2 crc32 atomics cpuid asimdrdm
