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Message-ID: <ced7dc06-bbc9-afa1-6973-b992871eac11@gmail.com>
Date:   Thu, 13 Jul 2023 09:24:58 +0800
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Subject: Re: [PATCH] riscv: correct pt_level name via pgtable_l5/4_enabled
To:     Palmer Dabbelt <palmer@dabbelt.com>, alex@ghiti.fr
Cc:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        alexghiti@rivosinc.com, Bjorn Topel <bjorn@rivosinc.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
References: <mhng-05add620-8132-496a-a514-4b78c78b3694@palmer-ri-x1c9a>
From:   Song Shuai <suagrfillet@gmail.com>
In-Reply-To: <mhng-05add620-8132-496a-a514-4b78c78b3694@palmer-ri-x1c9a>
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在 2023/7/12 21:58, Palmer Dabbelt 写道:
> On Tue, 11 Jul 2023 04:14:10 PDT (-0700), alex@ghiti.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@gmail.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@rivosinc.com>
> 
> Thanks.
> 
> Song: do you have a v2 that addresses the comments?
> 
Here is V2 :

https://lore.kernel.org/linux-riscv/20230712115740.943324-1-suagrfillet@gmail.com/
>>
>> Thanks,
>>
>> Alex

-- 
Thanks
Song Shuai