[HELP] How to print MMU related information on ARM FVP?

[lzc1001]

Description

I want to print virtual address and physical address when initialize MMU in arm64_mmu.c. So, I set CONFIG_MMU_DEBUG = 1 and set other configuration as following picture.

But the related mmu configuration information do not print.
Thanks for everyone!

Verification

• I have verified before submitting the report.

[acassis]

@lzc1001 look inside arch/arm64/src/common/arm64_mmu.c the virtual and physical addresses are no printed by default, you need to add a new "sinfo()" with that values you want to print

[lzc1001]

@acassis Thanks for your answer!😀 So, I need to write a new "sinfo()" by myself? Because I found that this function was already written in the code, but it was wrapped in the macro.

[acassis]

@lzc1001 hmm, I think I discovered the issue: there is not CONFIG_MMU_DEBUG.
Just run: $ git grep MMU_DEBUG

There need to exist an MMU_DEBUG symbol defined inside a Kconfig or you can just comment out these lines:

/* MMU debug option
 * #define CONFIG_MMU_ASSERT 1
 * #define CONFIG_MMU_DEBUG 1
 * #define CONFIG_MMU_DUMP_PTE 1
 */

[acassis]

@lzc1001 if you get it working, please close this Issue

[lzc1001]

@acassis i add "#define CONFIG_MMU_DEBUG 1" to arch/arm64/src/common/arm64_mmu.c, then run on FVP. But the related mmu information still do not print.😫

[acassis]

@lupyuen any idea?

[lupyuen]

Hi @lzc1001 you mentioned FVP, could you verify that this is the Build Config that we used?

$ tools/configure.sh fvp-armv8r:nsh

fvp-armv8r:nsh doesn't seem to support MMU. Maybe that's why the MMU Logging wasn't working?

$ grep MMU .config
# CONFIG_ARCH_HAVE_MMU is not set

I tried qemu-armv8a:nsh, but it doesn't support MMU either:

$ ./tools/configure.sh qemu-armv8a:nsh
$ grep MMU .config
CONFIG_ARCH_HAVE_MMU=y
# CONFIG_ARCH_USE_MMU is not set

Update: Sorry I forgot to enable Scheduler Info Logging for QEMU, now I can see the MMU Log for QEMU.

Here's how I enabled logging MMU Logging in arch/arm64/src/common/arm64_mmu.c:

/***************************************************************************
 * Pre-processor Definitions
 ***************************************************************************/

// Uncommented the MMU debug options
#define CONFIG_MMU_ASSERT 1
#define CONFIG_MMU_DEBUG 1
#define CONFIG_MMU_DUMP_PTE 1

// CONFIG_MMU_ASSERT needs this
#define trace_printf sinfo

// Existing code below...
#ifdef CONFIG_MMU_DEBUG

And here's the MMU Log for QEMU:

$ ./tools/configure.sh -l qemu-armv8a:nsh
$ make menuconfig
## TODO: Enable Scheduler Info Logging
$ make
$ qemu-system-aarch64 -cpu cortex-a53 -nographic \
     -machine virt,virtualization=on,gic-version=3 \
     -net none -chardev stdio,id=con,mux=on -serial chardev:con \
     -mon chardev=con,mode=readline -kernel ./nuttx

arm64_mmu_init: xlat tables:
arm64_mmu_init: base table(L1): 0x403c5000, 64 entries
arm64_mmu_init: 0: 0x403be000
arm64_mmu_init: 1: 0x403bf000
arm64_mmu_init: 2: 0x403c0000
arm64_mmu_init: 3: 0x403c1000
arm64_mmu_init: 4: 0x403c2000
arm64_mmu_init: 5: 0x403c3000
arm64_mmu_init: 6: 0x403c4000
init_xlat_tables: mmap: virt 117440512x phys 117440512x size 536870912x

Could you verify that MMU is enabled for NuttX on FVP? Thanks.

[lzc1001]

@lupyuen Thanks for your answer! I ported NuttX to A53 based on FVP in the last few days and ARM A53 have MMU. Then, NuttX can boot and input command to terminal, like "ls", "hello", etc. So, I think MMU is enabled for NuttX on FVP. But I do't make sure that the porting code have some potential bug, hhh😀.
According to your answer, I add code to arch/arm64/src/common/arm64_mmu.c and enable the related congfiguration by menuconfig. But the MMU infnormation still do not print. Maybe porting code have other issues. I will check my added code. The NuttX commit ID is 7a865b2, tag: nuttx-12.6.0-RC1
Thank you very much again！

[lupyuen]

@lzc1001 Can you verify that the NuttX Config supports MMU?

$ grep MMU .config
CONFIG_ARCH_HAVE_MMU=y
# CONFIG_ARCH_USE_MMU is not set

Is it possible that the MMU code is disabled due to other reasons? Perhaps we can add an Error Message in arch/arm64/src/common/arm64_mmu.c:

int arm64_mmu_init(bool is_primary_core)
{
#error MMU is enabled
...

[lzc1001]

@lupyuen Yes! The config support MMU

[lupyuen]

@lzc1001 I wonder if sinfo is failing to log correctly. What if you rename all sinfo to _info?

[raiden00pl]

arm64_mmu_init() is called early in arm64_chip_boot() so it's possible that serial console is not yet initialized. arm64_earlyserialinit() is called after arm64_mmu_init(). You can add simple debug message (_info("xxxx")) at the top of arm64_chip_boot() and after arm64_mmu_init() to see if serial port works at this boot stage.

[acassis]

@raiden00pl @lupyuen @lzc1001 maybe RAMLOG could solve this issue.

[raiden00pl]

@acassis RAMLOG is registered also late in boot process (in drivers_initialize()). One option if serial is not available since boot and requires some kind of initialization is to separate arm64_mmu_init() from MMU debug dump functionality like it's done for ACPI in x86:

1. ACPI is parsed in early boot stage in __nxstart() as it's required for other initialization tasks
2. ACPI dump is done in up_initialize() when some low-level initialization is already done (like x86_64_serialinit())