linux-kernel - Re: [PATCH v2 4/6] arm64: Utilize phys_initrd_start/phys_initrd

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Message-Id: <20181031070350.GA12503@rapoport-lnx>
Date:   Wed, 31 Oct 2018 09:03:50 +0200
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Robin Murphy <robin.murphy@....com>,
        Laura Abbott <labbott@...hat.com>,
        Stefan Agner <stefan@...er.ch>,
        Johannes Weiner <hannes@...xchg.org>,
        Greg Hackmann <ghackmann@...roid.com>,
        Kristina Martsenko <kristina.martsenko@....com>,
        CHANDAN VN <chandan.vn@...sung.com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>, linux@...linux.org.uk,
        green.hu@...il.com, deanbo422@...il.com, gxt@....edu.cn,
        ard.biesheuvel@...aro.org, linux-snps-arc@...ts.infradead.org,
        vgupta@...opsys.com
Subject: Re: [PATCH v2 4/6] arm64: Utilize phys_initrd_start/phys_initrd_size

On Tue, Oct 30, 2018 at 04:07:19PM -0700, Florian Fainelli wrote:
> ARM64 is the only architecture that re-defines
> __early_init_dt_declare_initrd() in order for that function to populate
> initrd_start/initrd_end with physical addresses instead of virtual
> addresses. Instead of having an override we can leverage
> drivers/of/fdt.c populating phys_initrd_start/phys_initrd_size to
> populate those variables for us.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  arch/arm64/mm/init.c | 21 +++++++++------------
>  1 file changed, 9 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 3cf87341859f..e95cee656a55 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -72,8 +72,8 @@ static int __init early_initrd(char *p)
>  	if (*endp == ',') {
>  		size = memparse(endp + 1, NULL);
>  
> -		initrd_start = start;
> -		initrd_end = start + size;
> +		phys_initrd_start = start;
> +		phys_initrd_size = size;
>  	}
>  	return 0;
>  }
> @@ -408,14 +408,14 @@ void __init arm64_memblock_init(void)
>  		memblock_add(__pa_symbol(_text), (u64)(_end - _text));
>  	}
>  
> -	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) {
> +	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
>  		/*
>  		 * Add back the memory we just removed if it results in the
>  		 * initrd to become inaccessible via the linear mapping.
>  		 * Otherwise, this is a no-op
>  		 */
> -		u64 base = initrd_start & PAGE_MASK;
> -		u64 size = PAGE_ALIGN(initrd_end) - base;
> +		u64 base = phys_initrd_start & PAGE_MASK;
> +		u64 size = PAGE_ALIGN(phys_initrd_size);
>  
>  		/*
>  		 * We can only add back the initrd memory if we don't end up
> @@ -460,13 +460,10 @@ void __init arm64_memblock_init(void)
>  	 */
>  	memblock_reserve(__pa_symbol(_text), _end - _text);
>  #ifdef CONFIG_BLK_DEV_INITRD
> -	if (initrd_start) {

There may be no initrd at all, so the condition here would rather become

	if (phys_initrd_start)

> -		memblock_reserve(initrd_start, initrd_end - initrd_start);
> -
> -		/* the generic initrd code expects virtual addresses */
> -		initrd_start = __phys_to_virt(initrd_start);
> -		initrd_end = __phys_to_virt(initrd_end);
> -	}
> +	/* the generic initrd code expects virtual addresses */
> +	initrd_start = __phys_to_virt(phys_initrd_start);
> +	initrd_end = initrd_start + phys_initrd_size;
> +	initrd_below_start_ok = 0;
>  #endif

I also wonder what is the reason to keep memstart_addr randomization and
initrd setup interleaved?

What we have now is roughly:

1) set memstart_addr
2) enforce memory_limit
3) reserve initrd
4) randomize memstart_addr
5) reserve text + data
6) reserve initrd again and set virtual addresses of initrd_{start,end}

Maybe it's possible to merge (3) into (6) ?

>  	early_init_fdt_scan_reserved_mem();
> -- 
> 2.17.1
> 

-- 
Sincerely yours,
Mike.