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Subject: Re: [PATCH AUTOSEL 4.9 05/10] sparc32: Limit memblock allocation to
 low memory
To:     Sasha Levin <sashal@kernel.org>, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Cc:     Mike Rapoport <rppt@linux.ibm.com>,
        "David S . Miller" <davem@davemloft.net>,
        sparclinux@vger.kernel.org
References: <20210302115921.63636-1-sashal@kernel.org>
 <20210302115921.63636-5-sashal@kernel.org>
From:   Andreas Larsson <andreas@gaisler.com>
Message-ID: <0b1dc8c7-2594-00ef-c117-a111e56f9c61@gaisler.com>
Date:   Wed, 3 Mar 2021 09:20:39 +0100
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On 2021-03-02 12:59, Sasha Levin wrote:
> From: Andreas Larsson <andreas@gaisler.com>
> 
> [ Upstream commit bda166930c37604ffa93f2425426af6921ec575a ]
> 
> Commit cca079ef8ac29a7c02192d2bad2ffe4c0c5ffdd0 changed sparc32 to use
> memblocks instead of bootmem, but also made high memory available via
> memblock allocation which does not work together with e.g. phys_to_virt
> and can lead to kernel panic.
> 
> This changes back to only low memory being allocatable in the early
> stages, now using memblock allocation.
> 
> Signed-off-by: Andreas Larsson <andreas@gaisler.com>
> Acked-by: Mike Rapoport <rppt@linux.ibm.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   arch/sparc/mm/init_32.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/arch/sparc/mm/init_32.c b/arch/sparc/mm/init_32.c
> index 3b7092d9ea8f..4abe4bf08377 100644
> --- a/arch/sparc/mm/init_32.c
> +++ b/arch/sparc/mm/init_32.c
> @@ -240,6 +240,9 @@ unsigned long __init bootmem_init(unsigned long *pages_avail)
>   	reserve_bootmem((bootmap_pfn << PAGE_SHIFT), size, BOOTMEM_DEFAULT);
>   	*pages_avail -= PAGE_ALIGN(size) >> PAGE_SHIFT;
>   
> +	/* Only allow low memory to be allocated via memblock allocation */
> +	memblock_set_current_limit(max_low_pfn << PAGE_SHIFT);
> +
>   	return max_pfn;
>   }
>   
> 

This is not needed for 4.9, and will not compile, as the problem it
fixes was introduced in 4.19.

-- 
Andreas Larsson