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

From: Andrew Jones <ajones@ventanamicro.com>
To: 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 10:43:06 +0100	[thread overview]
Message-ID: <20230313094306.6kslmrdixuw75iqf@orel> (raw)
In-Reply-To: <20230310094539.764357-4-alexghiti@rivosinc.com>

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.

> -	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?

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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