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Date:   Wed, 5 Jul 2023 18:19:47 +0800
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Subject: Re: [PATCH] riscv: Start of DRAM should at least be aligned on PMD
 size for the direct mapping
To:     Alexandre Ghiti <alexghiti@rivosinc.com>,
        Conor Dooley <conor.dooley@microchip.com>
Cc:     Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230704121837.248976-1-alexghiti@rivosinc.com>
 <20230704-emblem-rubble-e4a3a87cb98e@wendy>
 <CAHVXubikF36Tc19vv9osVz3ZvEyKXk-+74YBpPAZQpSt+vFkQw@mail.gmail.com>
From:   Song Shuai <suagrfillet@gmail.com>
In-Reply-To: <CAHVXubikF36Tc19vv9osVz3ZvEyKXk-+74YBpPAZQpSt+vFkQw@mail.gmail.com>
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在 2023/7/4 21:16, Alexandre Ghiti 写道:
> On Tue, Jul 4, 2023 at 2:26 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>>
>> Hey Alex,
>>
>> On Tue, Jul 04, 2023 at 02:18:37PM +0200, Alexandre Ghiti wrote:
>>> So that we do not end up mapping the whole linear mapping using 4K
>>> pages, which is slow at boot time, and also very likely at runtime.
>>>
>>> So make sure we align the start of DRAM on a PMD boundary.
>>>
>>> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>>
>> Obviously correct me if I am wrong here, but was this not reported by
>> Song Shuai as a regression?
>> Accordingly, should this not have Reported-by, Closes/Link & Fixes tags?
> 
> Sure we should add the reported by from Song as he did the proper report :)
> 
> Reported-by: Song Shuai <suagrfillet@gmail.com>
> Closes: https://lore.kernel.org/linux-riscv/20230625140931.1266216-1-songshuaishuai@tinylab.org/
> 
> And yes sorry, I thought it was there before, but it was actually when
> I retrieved the first 2MB that the problem appeared, so:
> 
> Fixes: 3335068f8721 ("riscv: Use PUD/P4D/PGD pages for the linear mapping")
> 
> Thanks!
And you can add my tested-by:

Tested-by: Song Shuai <suagrfillet@gmail.com>
> 
>>
>> Cheers,
>> Conor.
>>
>>> ---
>>>   arch/riscv/mm/init.c | 7 ++++++-
>>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>> index 4fa420faa780..4a43ec275c6d 100644
>>> --- a/arch/riscv/mm/init.c
>>> +++ b/arch/riscv/mm/init.c
>>> @@ -214,8 +214,13 @@ static void __init setup_bootmem(void)
>>>        memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
>>>
>>>        phys_ram_end = memblock_end_of_DRAM();
>>> +
>>> +     /*
>>> +      * Make sure we align the start of the memory on a PMD boundary so that
>>> +      * at worst, we map the linear mapping with PMD mappings.
>>> +      */
>>>        if (!IS_ENABLED(CONFIG_XIP_KERNEL))
>>> -             phys_ram_base = memblock_start_of_DRAM();
>>> +             phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
>>>
>>>        /*
>>>         * In 64-bit, any use of __va/__pa before this point is wrong as we
>>> --
>>> 2.39.2
>>>

-- 
Thanks
Song Shuai