linux-kernel - Re: [PATCH v5 3/4] arm64: use both ZONE_DMA and ZONE

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Date:   Wed, 11 Sep 2019 12:54:38 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     catalin.marinas@....com, hch@....de, wahrenst@....net,
        marc.zyngier@....com, robh+dt@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org, Will Deacon <will@...nel.org>
Cc:     f.fainelli@...il.com, robin.murphy@....com,
        linux-kernel@...r.kernel.org, mbrugger@...e.com,
        linux-rpi-kernel@...ts.infradead.org, phill@...pberrypi.org,
        m.szyprowski@...sung.com
Subject: Re: [PATCH v5 3/4] arm64: use both ZONE_DMA and ZONE_DMA32

On Mon, 2019-09-09 at 11:58 +0200, Nicolas Saenz Julienne wrote:
> +
>  /*
> - * Return the maximum physical address for ZONE_DMA32 (DMA_BIT_MASK(32)). It
> - * currently assumes that for memory starting above 4G, 32-bit devices will
> - * use a DMA offset.
> + * Return the maximum physical address for a zone with a given address size
> + * limit. It currently assumes that for memory starting above 4G, 32-bit
> + * devices will use a DMA offset.
>   */
> -static phys_addr_t __init max_zone_dma32_phys(void)
> +static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
>  {
>         phys_addr_t offset = memblock_start_of_DRAM() & GENMASK_ULL(63, 32);
> -       return min(offset + (1ULL << 32), memblock_end_of_DRAM());
> +       return min(offset + (1ULL << zone_bits), memblock_end_of_DRAM());
>  }

Hi all,
while testing other code on top of this series on odd arm64 machines I found an
issue: when memblock_start_of_DRAM() != 0, max_zone_phys() isn't taking into
account the offset to the beginning of memory. This doesn't matter with
zone_bits == 32 but it does when zone_bits == 30.

I'll send a follow-up series.

Regards,
Nicolas


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