Revert "dma-contiguous: check for memory region overlap"
authorZhenhua Huang <quic_zhenhuah@quicinc.com>
Thu, 7 Sep 2023 08:03:56 +0000 (16:03 +0800)
committerChristoph Hellwig <hch@lst.de>
Fri, 8 Sep 2023 08:58:32 +0000 (05:58 -0300)
commitf875db4f20f4ec2e4fa3b3be0e5081976e0b5dad
treedd809d3d3467b37495982ce735fe5e9b500bc4c4
parent765aa6b3a462ed69ddcb1c41a6f7f93b8abb7d43
Revert "dma-contiguous: check for memory region overlap"

This reverts commit 3fa6456ebe13adab3ba1817c8e515a5b88f95dce.

The Commit broke the CMA region creation through DT on arm64,
as showed below logs with "memblock=debug":
[    0.000000] memblock_phys_alloc_range: 41943040 bytes align=0x200000
from=0x0000000000000000 max_addr=0x00000000ffffffff
early_init_dt_alloc_reserved_memory_arch+0x34/0xa0
[    0.000000] memblock_reserve: [0x00000000fd600000-0x00000000ffdfffff]
memblock_alloc_range_nid+0xc0/0x19c
[    0.000000] Reserved memory: overlap with other memblock reserved region

>From call flow, region we defined in DT was always reserved before entering
into rmem_cma_setup. Also, rmem_cma_setup has one routine cma_init_reserved_mem
to ensure the region was reserved. Checking the region not reserved here seems
not correct.

early_init_fdt_scan_reserved_mem:
    fdt_scan_reserved_mem
        __reserved_mem_reserve_reg
early_init_dt_reserve_memory
memblock_reserve(using “reg” prop case)
        fdt_init_reserved_mem
__reserved_mem_alloc_size
*early_init_dt_alloc_reserved_memory_arch*
memblock_reserve(dynamic alloc case)
        __reserved_mem_init_node
rmem_cma_setup(region overlap check here should always fail)

Example DT can be used to reproduce issue:

    dump_mem: mem_dump_region {
            compatible = "shared-dma-pool";
            alloc-ranges = <0x0 0x00000000 0x0 0xffffffff>;
            reusable;
            size = <0 0x2800000>;
    };

Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com>
kernel/dma/contiguous.c