linux-kernel - Re: [PATCH 3/3] dma-pool: limit DMA and DMA32 zone size pools

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Message-ID: <YwNx6Q+FSwpKUOQ2@dhcp22.suse.cz>
Date:   Mon, 22 Aug 2022 14:09:13 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux.dev, Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        David Rientjes <rientjes@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] dma-pool: limit DMA and DMA32 zone size pools

On Mon 22-08-22 13:14:47, Christoph Hellwig wrote:
> On Mon, Aug 22, 2022 at 10:41:01AM +0200, Michal Hocko wrote:
> > ZONE_DMA existance is not runtime controlable (at least on x86).
> 
> This is more about ZONE_DMA32 that can disappear if all memory is
> inside ZONE_DMA.  That is highly unusual (but still possible) with a
> tiny x86-style ZONE_DMA, but can happen with a larger one other
> architectures.

OK, so you are worried about configurations that lack ZONE_DMA32 because
that memory range is covered by ZONE_DMA? I thought though simply do not
have CONFIG_ZONE_DMA32. Or am I wrong here?

-- 
Michal Hocko
SUSE Labs