linux-kernel - Re: [PATCH] riscv: correct pt_level name via pgtable_l5/4

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Message-ID: <mhng-05add620-8132-496a-a514-4b78c78b3694@palmer-ri-x1c9a>
Date:   Wed, 12 Jul 2023 06:58:00 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     alex@...ti.fr, suagrfillet@...il.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        alexghiti@...osinc.com, Bjorn Topel <bjorn@...osinc.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject:     Re: [PATCH] riscv: correct pt_level name via pgtable_l5/4_enabled

On Tue, 11 Jul 2023 04:14:10 PDT (-0700), alex@...ti.fr wrote:
> Hi Song,
>
>
> On 11/07/2023 12:52, Song Shuai wrote:
>> The pt_level uses CONFIG_PGTABLE_LEVELS to display page table names.
>> But if downgrading page mode from kernel cmdline in 64BIT, it will
>> give a wrong name.
>>
>> Like, using no4lvl for sv39, ptdump named the 1G-mapping as "PUD"
>> that should be "PGD":
>>
>> 0xffffffd840000000-0xffffffd900000000    0x00000000c0000000         3G PUD     D A G . . W R V
>>
>> So select "P4D/PUD" or "PGD" via pgtable_l5/4_enabled to correct it.
>>
>> Fixes: 26e7aacb83df ("riscv: Allow to downgrade paging mode from the command line")
>> Signed-off-by: Song Shuai <suagrfillet@...il.com>
>> ---
>>   arch/riscv/mm/ptdump.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/riscv/mm/ptdump.c b/arch/riscv/mm/ptdump.c
>> index 20a9f991a6d7..cfdd327981ee 100644
>> --- a/arch/riscv/mm/ptdump.c
>> +++ b/arch/riscv/mm/ptdump.c
>> @@ -384,6 +384,11 @@ static int __init ptdump_init(void)
>>
>>   	kernel_ptd_info.base_addr = KERN_VIRT_START;
>>
>> +#ifdef CONFIG_64BIT
>> +	pg_level[1].name = pgtable_l5_enabled ? "P4D" : "PGD";
>> +	pg_level[2].name = pgtable_l4_enabled ? "PUD" : "PGD";
>> +#endif
>
>
> You don't need the #ifdef here as pgtable_lX_enabled are always declared.
>
>
>> +
>>   	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
>>   		for (j = 0; j < ARRAY_SIZE(pte_bits); j++)
>>   			pg_level[i].mask |= pte_bits[j].mask;
>
>
> The Fixes tag is wrong to me, if satp mode is restricted by the hardware
> itself (not from the command line), the same problem happens. Maybe that
> should be the sv48 introduction patch? Or the sv57? It will be more
> cumbersome to backport with the sv48 introduction though as this patch
> won't apply as-is.

Sometimes it's easier to base the fix on the original offending commit 
and then forward-port it via a merge, I haven't looked at this one to 
know for sure though.

> Otherwise, you can add:
>
> Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

Thanks.

Song: do you have a v2 that addresses the comments?

>
> Thanks,
>
> Alex