Re: [PATCH v7 3/4] arm64: Make use of memblock_isolate_memory for the linear mapping

From: Alexandre Ghiti <alex@ghiti.fr>
To: Andrew Jones <ajones@ventanamicro.com>,
	Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: 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>,
	Mike Rapoport <rppt@kernel.org>,
	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
Subject: Re: [PATCH v7 3/4] arm64: Make use of memblock_isolate_memory for the linear mapping
Date: Mon, 13 Mar 2023 11:01:33 +0100	[thread overview]
Message-ID: <77564d46-5bca-81b8-8e14-c70624ddce5e@ghiti.fr> (raw)
In-Reply-To: <20230313094306.6kslmrdixuw75iqf@orel>

Hi Andrew,

On 3/13/23 10:43, Andrew Jones wrote:
> On Fri, Mar 10, 2023 at 10:45:38AM +0100, Alexandre Ghiti wrote:
>> In order to isolate the kernel text mapping, we used some sort of hack
>> to isolate the kernel text range which consisted in marking this region
>> as not mappable with memblock_mark_nomap. Simply use the newly introduced
>> memblock_isolate_memory function which does exactly the same but does not
>> uselessly mark the region as not mappable.
>>
>> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>> ---
>>   arch/arm64/mm/mmu.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 6f9d8898a025..408dc852805c 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -552,7 +552,7 @@ static void __init map_mem(pgd_t *pgdp)
>>   	 * So temporarily mark them as NOMAP to skip mappings in
>>   	 * the following for-loop
>>   	 */
> The comment above doesn't apply anymore.

Yep, noticed this one after sending, thanks anyway!

>
>> -	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
>> +	memblock_isolate_memory(kernel_start, kernel_end - kernel_start);
>>   
>>   #ifdef CONFIG_KEXEC_CORE
>>   	if (crash_mem_map) {
>> @@ -568,6 +568,7 @@ static void __init map_mem(pgd_t *pgdp)
>>   	for_each_mem_range(i, &start, &end) {
>>   		if (start >= end)
>>   			break;
>> +
> Mark nomap is also used for the crash kernel. Does the new API not work
> for it?

Seems you're right, I missed it.

Thanks,

Alex

>
> Thanks,
> drew
>
>>   		/*
>>   		 * The linear map must allow allocation tags reading/writing
>>   		 * if MTE is present. Otherwise, it has the same attributes as
>> @@ -589,7 +590,6 @@ static void __init map_mem(pgd_t *pgdp)
>>   	 */
>>   	__map_memblock(pgdp, kernel_start, kernel_end,
>>   		       PAGE_KERNEL, NO_CONT_MAPPINGS);
>> -	memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
>>   
>>   	/*
>>   	 * Use page-level mappings here so that we can shrink the region
>> -- 
>> 2.37.2
>>
>>
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