64位ARMv8的芯片-reserved memory-mmu

基于64位ARMv8的一些AP芯片，支持32位和64位代码之间无缝运行(比如有芯片在用CortexA53 OCTA core)。

以之前做过的项目为例，说明64位芯片的寄存器，以及说明在64为模式下的内存地址表示和整个Linux系统的Memory Map。
以下是整个物理内存块的大小-起始地址，这个项目的内存地址是2GB。

ATAG_MEM: 4 54410002 20000000 40000000  //大小为20000000，开始地址为40000000 以此类推ATAG_MEM: 4 54410002 20000000 60000000ATAG_MEM: 4 54410002 20000000 80000000ATAG_MEM: 4 54410002 1EE00000 A0000000

项目的reserve memory，定义如下：

/memreserve/ 0xBEE00000 0x1200000;       /* EL3 monitor, secure intepreter *//memreserve/ 0xB0000000 0x7800000;  /* CP memory(128MB) + AP-CP shared memory(8MB) *// {    memory@40000000 {        device_type = "memory";        reg = <0x0 0x40000000 0x0 0x80000000>;    };    reserved-memory {        #address-cells = <2>;        #size-cells = <2>;        ranges;        fimc_is_fd_reserved: fimc_is_fd {            compatible = "fd-lib-shmem";            reg = <0x0 0xbe200000 0x0 0x100000>;        };        common {            compatible = "exynos5433-ion,common";            reg = <0x0 0xbdc00000 0x0 0x600000>;            id = <0>;        };        video {            compatible = "exynos5433-ion,video";            secure;            reusable;            reg = <0x0 0xb8400000 0x0 0x5800000>;            id = <11>;            compat-id = <4 5 6 7>;        };        video_ext {            compatible = "exynos5433-ion,video_ext";            secure;            reusable;            reg = <0x0 0xaec00000 0x0 0x1400000>;            id = <1>;        };        mfc_nfw {            compatible = "exynos5433-ion,mfc_nfw";            reg = <0x0 0xb8200000 0x0 0x110000>;            id = <12>;        };        mfc_fw {            compatible = "exynos5433-ion,mfc_fw";            secure;            reg = <0x0 0xb8000000 0x0 0x200000>;            id = <8>;        };        secdma {            compatible = "exynos5433-ion,secdma";            size = <0 0x20000>;            alignment = <0 0x10000>;            id = <13>;        };    };};

modem的reserve memory范围：

/ {    /* over-riding shared memory reserved map */    /* DRAM 2GB + CP reserved map 116+4MB */    shmem: shmem@0xB0000000 {        reg = <0x0 0xB0000000 0x0 0x7800000>;        shmem,ipc_offset = <0x7400000>;        shmem,ipc_size = <0x400000>;    };};

这些部分在哪里读取以及怎么设置需要再仔细分析。先来看一下输出的log。

<6>[0.000000][0:swapper:0] fimc_is_fd reserved memory: fimc_is_fd=0x100000@0x00000000be200000<7>[0.000000][0:swapper:0] [@][FD] vaddr: 0xffffffc07e200000<6>[0.000000][0:swapper:0] Reserved memory[1]: common:0x600000<6>[0.000000][0:swapper:0] Reserved memory: initialized node common, compatible id exynos5433-ion,common<6>[0.000000][0:swapper:0] cma: CMA: reserved 88 MiB at b8400000<6>[0.000000][0:swapper:0] CMA memory[12]: video:0x5800000<6>[0.000000][0:swapper:0] Reserved memory: initialized node video, compatible id exynos5433-ion,video<6>[0.000000][0:swapper:0] cma: CMA: reserved 20 MiB at aec00000<6>[0.000000][0:swapper:0] CMA memory[2]: video_ext:0x1400000<6>[0.000000][0:swapper:0] Reserved memory: initialized node video_ext, compatible id exynos5433-ion,video_ext<6>[0.000000][0:swapper:0] Reserved memory[13]: mfc_nfw:0x110000<6>[0.000000][0:swapper:0] Reserved memory: initialized node mfc_nfw, compatible id exynos5433-ion,mfc_nfw<6>[0.000000][0:swapper:0] Reserved memory[9]: mfc_fw:0x200000<6>[0.000000][0:swapper:0] Reserved memory: initialized node mfc_fw, compatible id exynos5433-ion,mfc_fw<6>[0.000000][0:swapper:0] Reserved memory[14]: secdma:0x20000<6>[0.000000][0:swapper:0] Reserved memory: initialized node secdma, compatible id exynos5433-ion,secdma

Virtual kernel memory layout如下：

<6>[0.000000][0:swapper:0] Memory: 2030MB = 2030MB total<5>[0.000000][0:swapper:0] Memory: 1754160k/1754160k available, 324560k reserved<5>[0.000000][0:swapper:0] Virtual kernel memory layout:<5>[0.000000][0:swapper:0]     vmalloc : 0xffffff8000000000 - 0xffffffbbffff0000   (245759 MB)<5>[0.000000][0:swapper:0]     vmemmap : 0xffffffbc00e00000 - 0xffffffbc029c1000   (    27 MB)<5>[0.000000][0:swapper:0]     modules : 0xffffffbffc000000 - 0xffffffc000000000   (    64 MB)<5>[0.000000][0:swapper:0]     memory  : 0xffffffc000000000 - 0xffffffc07ee00000   (  2030 MB)<5>[0.000000][0:swapper:0]       .init : 0xffffffc000cf8000 - 0xffffffc000da42c0   (   689 kB)<5>[0.000000][0:swapper:0]       .text : 0xffffffc000205000 - 0xffffffc000cf8000   ( 11212 kB)//Starting kernel at 0x40205000... 对应的虚拟内存是0xffffffc000205000<5>[0.000000][0:swapper:0]       .data : 0xffffffc000da5000 - 0xffffffc000ea8140   (  1037 kB)

ion memory配置错误会导致panic，比如：

<1>[0.833825]  [0:swapper/0:1] Unable to handle kernel paging request at virtual address ffffffc07f000000<1>[0.833864]  [0:swapper/0:1] pgd = ffffffc000202000<1>[0.833898]  [0:swapper/0:1] [ffffffc07f000000] *pgd=000000007ffff003, *pmd=0000000000000000<4>[0.834028]  [0:swapper/0:1] ------------[ cut here ]------------<2>[0.834062]  [0swapper/0:    1] Kernel BUG at ffffffc0002175fc [verbose debug info unavailable]

paging request错误的地址为ffffffc07f000000。算一下对应的物理地址是0xbf000000。但看一下atag信息，物理地址最大不能超过0xbee00000(ATAG_MEM: 4 54410002 1EE00000 A0000000)。看一下ion memory的配置，发现如下配置，改一下起始地址，保证不要超过物理地址范围即可:

    reserved-memory {        ...        common {            compatible = "exynos5433-ion,common";            reg = <0x0 0xbf000000 0x0 0x600000>;            id = <0>;        };        ...    }