Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <5e3dec6d-c3a1-1fdb-7c5a-e9b81cfde2b5@ghiti.fr>
Date:   Thu, 23 Mar 2023 13:30:25 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.8.0
Subject: Re: [PATCH v8 2/4] mm: Introduce memblock_isolate_memory
Content-Language: en-US
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Alexandre Ghiti <alexghiti@rivosinc.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anup Patel <anup@brainfault.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
        linux-mm@kvack.org
References: <20230316131711.1284451-1-alexghiti@rivosinc.com>
 <20230316131711.1284451-3-alexghiti@rivosinc.com>
 <ZBN4Hoo99DNd5wKx@kernel.org> <efe1ef6b-b1c2-8d5b-82b7-3cd64053643e@ghiti.fr>
 <ZBibYDR0h1UeL6L5@kernel.org> <67ba29ff-b03d-2d24-a844-7ae25ddca447@ghiti.fr>
 <ZBxDDPnldPIgKngc@kernel.org>
From:   Alexandre Ghiti <alex@ghiti.fr>
In-Reply-To: <ZBxDDPnldPIgKngc@kernel.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 3/23/23 13:16, Mike Rapoport wrote:
> On Thu, Mar 23, 2023 at 12:52:36PM +0100, Alexandre Ghiti wrote:
>> On 3/20/23 18:44, Mike Rapoport wrote:
>>> On Mon, Mar 20, 2023 at 11:54:14AM +0100, Alexandre Ghiti wrote:
>>>> Hi Mike,
>>>>
>>>> On 3/16/23 21:12, Mike Rapoport wrote:
>>>>> Hi Alexandre,
>>>>>
>>>>> On Thu, Mar 16, 2023 at 02:17:09PM +0100, Alexandre Ghiti wrote:
>>>>>> This function allows to split a region in memblock.memory and will be
>>>>>> useful when setting up the linear mapping with STRICT_KERNEL_RWX: it
>>>>>> allows to isolate the kernel text/rodata and then avoid to map those
>>>>>> regions with a PUD/P4D/PGD.
>>>>> Sorry I've missed it last time. The changelog is fine in the context of
>>>> No worries :)
>>>>
>>>>
>>>>> this series, but if you look at it as a part of memblock changelog it
>>>>> doesn't provide enough background on why memblock_isolate_memory() is
>>>>> useful.
>>>>>
>>>>> Can you please add more context so it would be self explanatory?
>>>> What about: "memblock.memory contains the list of memory regions and a
>>>> memory region can cover memory that will be mapped with different
>>>> permissions. So to ease the mapping process, allow to isolate those regions
>>>> by introducing a new function called memblock_isolate_memory. This will be
>>>> used in arch specific code to isolate the kernel text/rodata regions when
>>>> STRICT_KERNEL_RWX is enabled so that we avoid mapping them with PUD/P4D/PGD
>>>> mappings."
>>> With this change
>>>
>>> ... STRICT_KERNEL_RWX is enabled so that they can be mapped with base pages.
>>
>> Actually they will get mapped with PMD mappings :) I'll just append: "or PMD
>> mapping" to your sentence above if that's ok with you.
> Didn't read the rest of the patches :)
>
> .. STRICT_KERNEL_RWX is enabled so that they can be mapped with differently
> than the rest of the memory.
>
> Does it cover the usescases?


Yes, fine with me!

Thanks again


>
>>> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
>>
>> Thanks for your review,
>>
>> Alex
>>
>>
>>>> Thanks,
>>>>
>>>> Alex
>>>>
>>>>
>>>>>> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>>>>>> Reviewed-by: Anup Patel <anup@brainfault.org>
>>>>>> Tested-by: Anup Patel <anup@brainfault.org>
>>>>>> ---
>>>>>>     include/linux/memblock.h |  1 +
>>>>>>     mm/memblock.c            | 20 ++++++++++++++++++++
>>>>>>     2 files changed, 21 insertions(+)
>>>>>>
>>>>>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>>>>>> index 50ad19662a32..2f7ef97c0da7 100644
>>>>>> --- a/include/linux/memblock.h
>>>>>> +++ b/include/linux/memblock.h
>>>>>> @@ -125,6 +125,7 @@ int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
>>>>>>     int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
>>>>>>     int memblock_mark_nomap(phys_addr_t base, phys_addr_t size);
>>>>>>     int memblock_clear_nomap(phys_addr_t base, phys_addr_t size);
>>>>>> +int memblock_isolate_memory(phys_addr_t base, phys_addr_t size);
>>>>>>     void memblock_free_all(void);
>>>>>>     void memblock_free(void *ptr, size_t size);
>>>>>> diff --git a/mm/memblock.c b/mm/memblock.c
>>>>>> index 25fd0626a9e7..e8c651a37012 100644
>>>>>> --- a/mm/memblock.c
>>>>>> +++ b/mm/memblock.c
>>>>>> @@ -805,6 +805,26 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
>>>>>>     	return 0;
>>>>>>     }
>>>>>> +/**
>>>>>> + * memblock_isolate_memory - isolate given range in memblock.memory
>>>>>> + * @base: base of range to isolate
>>>>>> + * @size: size of range to isolate
>>>>>> + *
>>>>>> + * Isolates the given range in memblock.memory so that it does not share any
>>>>>> + * region with other ranges.
>>>>>> + *
>>>>>> + * Return:
>>>>>> + * 0 on success, -errno on failure.
>>>>>> + */
>>>>>> +
>>>>>> +int __init_memblock memblock_isolate_memory(phys_addr_t base, phys_addr_t size)
>>>>>> +{
>>>>>> +	int start_rgn, end_rgn;
>>>>>> +
>>>>>> +	return memblock_isolate_range(&memblock.memory, base, size,
>>>>>> +				      &start_rgn, &end_rgn);
>>>>>> +}
>>>>>> +
>>>>>>     static int __init_memblock memblock_remove_range(struct memblock_type *type,
>>>>>>     					  phys_addr_t base, phys_addr_t size)
>>>>>>     {
>>>>>> -- 
>>>>>> 2.37.2
>>>>>>