linux-kernel - Re: [PATCH V3 2/3] arm64: support initrd outside kernel linear map

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Message-ID: <20150817112256.GH1688@arm.com>
Date:	Mon, 17 Aug 2015 12:22:56 +0100
From:	Will Deacon <will.deacon@....com>
To:	Mark Salter <msalter@...hat.com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"x86@...nel.org" <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Mark Rutland <Mark.Rutland@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH V3 2/3] arm64: support initrd outside kernel linear map

Hi Mark,

On Sun, Aug 16, 2015 at 09:49:27PM +0100, Mark Salter wrote:
> The use of mem= could leave part or all of the initrd outside of
> the kernel linear map. This will lead to an error when unpacking
> the initrd and a probable failure to boot. This patch catches that
> situation and relocates the initrd to be fully within the linear
> map.
> 
> Signed-off-by: Mark Salter <msalter@...hat.com>
> ---
>  arch/arm64/kernel/setup.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
> 
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index f3067d4..5f45fd9 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -359,6 +359,64 @@ static void __init request_standard_resources(void)
>  	}
>  }
>  
> +#ifdef CONFIG_BLK_DEV_INITRD
> +/*
> + * Relocate initrd if it is not completely within the linear mapping.
> + * This would be the case if mem= cuts out all or part of it.
> + */
> +static void __init relocate_initrd(void)
> +{
> +	phys_addr_t orig_start = __virt_to_phys(initrd_start);
> +	phys_addr_t orig_end = __virt_to_phys(initrd_end);

Any particular reason to use the __* variants here?

> +	phys_addr_t ram_end = memblock_end_of_DRAM();
> +	phys_addr_t new_start;
> +	unsigned long size, to_free = 0;
> +	void *dest;
> +
> +	if (orig_end <= ram_end)
> +		return;
> +
> +	/* Note if any of original initrd will freeing below */

The comment doesn't make sense.

> +	if (orig_start < ram_end)
> +		to_free = ram_end - orig_start;
> +
> +	size = orig_end - orig_start;
> +
> +	/* initrd needs to be relocated completely inside linear mapping */
> +	new_start = memblock_find_in_range(0, PFN_PHYS(max_pfn),
> +					   size, PAGE_SIZE);
> +	if (!new_start)
> +		panic("Cannot relocate initrd of size %ld\n", size);
> +	memblock_reserve(new_start, size);
> +
> +	initrd_start = __phys_to_virt(new_start);
> +	initrd_end   = initrd_start + size;
> +
> +	pr_info("Moving initrd from [%llx-%llx] to [%llx-%llx]\n",
> +		orig_start, orig_start + size - 1,
> +		new_start, new_start + size - 1);
> +
> +	dest = (void *)initrd_start;
> +
> +	if (to_free) {
> +		memcpy(dest, (void *)__phys_to_virt(orig_start), to_free);
> +		dest += to_free;
> +	}
> +
> +	copy_from_early_mem(dest, orig_start + to_free, size - to_free);
> +
> +	if (to_free) {
> +		pr_info("Freeing original RAMDISK from [%llx-%llx]\n",
> +			orig_start, orig_start + to_free - 1);
> +		memblock_free(orig_start, to_free);
> +	}
> +}
> +#else
> +static inline void __init reserve_initrd(void)

relocate_initrd ?

Will
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