Re: [Crash-utility] RISCV64: Use va_kernel_pa_offset in VTOP()

[Song Shuai <suagrfillet@gmail.com>]

在 2023/8/4 12:42, HAGIO KAZUHITO(萩尾 一仁) 写道:
> On 2023/07/24 13:06, Song Shuai wrote:
>> Since RISC-V Linux v6.4, the commit 3335068f8721 ("riscv: Use
>> PUD/P4D/PGD pages for the linear mapping") changes the
>> phys_ram_base from the kernel_map.phys_addr to the start of DRAM.
>>
>> The Crash's VTOP() still uses phys_ram_base and kernel_map.virt_addr
>> to translate kernel virtual address, that made Crash boot failed with
>> Linux v6.4 and later version.
>>
>> Let Linux export kernel_map.va_kernel_pa_offset in v6.5 and Crash can
>> use "va_kernel_pa_offset" to translate the kernel virtual address in
>> VTOP() correctly.
>>
>> Signed-off-by: Song Shuai <suagrfillet@gmail.com>
>> ---
>> You can check/test the Linux changes from this link:
>> https://github.com/sugarfillet/linux/commits/6.5-rc3-crash
>>
>> And I'll send the Linux changes to riscv/for-next If you're ok with this patch.
>> ---
>>    defs.h    |  4 ++--
>>    riscv64.c | 22 ++++++++++++++++++++++
>>    2 files changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/defs.h b/defs.h
>> index 358f365..46b9857 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -3662,8 +3662,7 @@ typedef signed int s32;
>>    	ulong _X = X;									\
>>    	(THIS_KERNEL_VERSION >= LINUX(5,13,0) &&					\
>>    		(_X) >= machdep->machspec->kernel_link_addr) ?				\
>> -		(((unsigned long)(_X)-(machdep->machspec->kernel_link_addr)) +		\
>> -		 machdep->machspec->phys_base):						\
>> +		((unsigned long)(_X)-(machdep->machspec->va_kernel_pa_offset)): 	\
>>    		(((unsigned long)(_X)-(machdep->kvbase)) +				\
>>    		 machdep->machspec->phys_base);						\
>>    	})
>> @@ -7021,6 +7020,7 @@ struct machine_specific {
>>    	ulong modules_vaddr;
>>    	ulong modules_end;
>>    	ulong kernel_link_addr;
>> +	ulong va_kernel_pa_offset;
>>    
>>    	ulong _page_present;
>>    	ulong _page_read;
>> diff --git a/riscv64.c b/riscv64.c
>> index 6b9a688..b9e50b4 100644
>> --- a/riscv64.c
>> +++ b/riscv64.c
>> @@ -418,6 +418,27 @@ error:
>>    	error(FATAL, "cannot get vm layout\n");
>>    }
>>    
>> +static void
>> +riscv64_get_va_kernel_pa_offset(struct machine_specific *ms)
>> +{
>> +	unsigned long kernel_version = riscv64_get_kernel_version();
>> +
>> +	/*
>> +	 * va_kernel_pa_offset is defined in Linux kernel since 6.5.
>> +	 */
>> +	if (kernel_version >= LINUX(6,5,0)) {
> 
> The kernel patches look accepted, so for the crash patch detail,
> 
> I think this first version check is not necessary, we can just use the
> vmcoreinfo entry if available.  With it, backporting the kernel patches
> to e.g. 6.4.0 will also be supported.
> 
ok, V2 is here:

https://lore.kernel.org/linux-riscv/20230804091559.3005820-1-suagrfillet@gmail.com/T/#u

> Thanks,
> Kazu
> 
>> +		char *string;
>> +		if ((string = pc->read_vmcoreinfo("NUMBER(va_kernel_pa_offset)"))) {
>> +			ms->va_kernel_pa_offset = htol(string, QUIET, NULL);
>> +			free(string);
>> +		} else
>> +			error(FATAL, "cannot read va_kernel_pa_offset\n");
>> +	} else if (kernel_version >= LINUX(6,4,0))
>> +		error(FATAL, "cannot determine va_kernel_pa_offset since Linux 6.4\n");
>> +	else
>> +		ms->va_kernel_pa_offset = ms->kernel_link_addr - ms->phys_base;
>> +}
>> +
>>    static int
>>    riscv64_is_kvaddr(ulong vaddr)
>>    {
>> @@ -1352,6 +1373,7 @@ riscv64_init(int when)
>>    		riscv64_get_struct_page_size(machdep->machspec);
>>    		riscv64_get_va_bits(machdep->machspec);
>>    		riscv64_get_va_range(machdep->machspec);
>> +		riscv64_get_va_kernel_pa_offset(machdep->machspec);
>>    
>>    		pt_level_alloc(&machdep->pgd, "cannot malloc pgd space.");
>>    		pt_level_alloc(&machdep->machspec->p4d, "cannot malloc p4d space.");

-- 
Thanks
Song Shuai

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