linux-kernel - Re: [PATCH v4 2/2] dma: replace zone_dma_bits by zone_dma

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Message-ID: <Zqtj1iCyRJqh_xeL@arm.com>
Date: Thu, 1 Aug 2024 11:30:46 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Baruch Siach <baruch@...s.co.il>
Cc: Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org,
	Petr Tesařík <petr@...arici.cz>,
	Ramon Fried <ramon@...reality.ai>,
	Elad Nachman <enachman@...vell.com>
Subject: Re: [PATCH v4 2/2] dma: replace zone_dma_bits by zone_dma_limit

On Thu, Aug 01, 2024 at 11:25:07AM +0300, Baruch Siach wrote:
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index d10613eb0f63..a6e15db9d1e7 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -70,9 +70,10 @@ static bool cma_in_zone(gfp_t gfp)
>  	/* CMA can't cross zone boundaries, see cma_activate_area() */
>  	end = cma_get_base(cma) + size - 1;
>  	if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA))
> -		return end <= DMA_BIT_MASK(zone_dma_bits);
> +		return end <= zone_dma_limit;
> +	/* Account for possible zone_dma_limit > DMA_BIT_MASK(32) */
>  	if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32))
> -		return end <= DMA_BIT_MASK(32);
> +		return end <= DMA_BIT_MASK(32) || end <= zone_dma_limit;
>  	return true;
>  }
>  
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 043b0ecd3e8d..53595eb41922 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -450,7 +450,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>  	if (!remap)
>  		io_tlb_default_mem.can_grow = true;
>  	if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp_mask & __GFP_DMA))
> -		io_tlb_default_mem.phys_limit = DMA_BIT_MASK(zone_dma_bits);
> +		io_tlb_default_mem.phys_limit = zone_dma_limit;
>  	else if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp_mask & __GFP_DMA32))
>  		io_tlb_default_mem.phys_limit = DMA_BIT_MASK(32);

I think this needs some adjustment as the cma_in_zone() case. Maybe just
use max(DMA_BIT_MASK(32), zone_dma_limit) in both cases for consistency.

-- 
Catalin