linux-kernel - Re: [PATCH] arm64: use generic free_initrd

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Message-ID: <0ba20aa4-d2dd-2263-6b5f-16a5c8a39f67@redhat.com>
Date:   Mon, 16 Sep 2019 08:23:29 -0400
From:   Laura Abbott <labbott@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH] arm64: use generic free_initrd_mem()

On 9/16/19 8:21 AM, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> arm64 calls memblock_free() for the initrd area in its implementation of
> free_initrd_mem(), but this call has no actual effect that late in the boot
> process. By the time initrd is freed, all the reserved memory is managed by
> the page allocator and the memblock.reserved is unused, so there is no
> point to update it.
> 

People like to use memblock for keeping track of memory even if it has no
actual effect. We made this change explicitly (see 05c58752f9dc ("arm64: To remove
initrd reserved area entry from memblock") That said, moving to the generic
APIs would be nice. Maybe we can find another place to update the accounting?

> Without the memblock_free() call the only difference between arm64 and the
> generic versions of free_initrd_mem() is the memory poisoning. Switching
> arm64 to the generic version will enable the poisoning.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
> 
> I've boot tested it on qemu and I've checked that kexec works.
> 
>   arch/arm64/mm/init.c | 8 --------
>   1 file changed, 8 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index f3c7952..8ad2934 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -567,14 +567,6 @@ void free_initmem(void)
>   	unmap_kernel_range((u64)__init_begin, (u64)(__init_end - __init_begin));
>   }
>   
> -#ifdef CONFIG_BLK_DEV_INITRD
> -void __init free_initrd_mem(unsigned long start, unsigned long end)
> -{
> -	free_reserved_area((void *)start, (void *)end, 0, "initrd");
> -	memblock_free(__virt_to_phys(start), end - start);
> -}
> -#endif
> -
>   /*
>    * Dump out memory limit information on panic.
>    */
>