linux-kernel - Re: [PATCH] dmaengine: ioat: Allocate correct size for descriptor chunk

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Date:   Tue, 22 Sep 2020 13:18:13 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Logan Gunthorpe <logang@...tatee.com>, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Robin Murphy <robin.murphy@....com>, Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] dmaengine: ioat: Allocate correct size for descriptor
 chunk



On 9/22/2020 1:08 PM, Logan Gunthorpe wrote:
> dma_alloc_coherent() is called with a fixed SZ_2M size, but frees happen
> with IOAT_CHUNK_SIZE. Recently, IOAT_CHUNK_SIZE was reduced to 512M but
> the allocation did not change. To fix, change to using the
> IOAT_CHUNK_SIZE define.
> 
> This was caught with the upcoming patchset for converting Intel platforms to the
> dma-iommu implementation. It has a warning when the unmapped size differs from
> the mapped size.
> 
> Fixes: a02254f8a676 ("dmaengine: ioat: Decreasing allocation chunk size 2M->512K")
> Link: https://lore.kernel.org/intel-gfx/776771a2-247a-d1be-d882-bee02d919ae0@deltatee.com/
> Suggested-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Cc: Vinod Koul <vkoul@...nel.org>
> Cc: Dave Jiang <dave.jiang@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>

Acked-by: Dave Jiang <dave.jiang@...el.com>

Thanks Logan.

> ---
>   drivers/dma/ioat/dma.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
> index a814b200299b..07296171e2bb 100644
> --- a/drivers/dma/ioat/dma.c
> +++ b/drivers/dma/ioat/dma.c
> @@ -389,7 +389,7 @@ ioat_alloc_ring(struct dma_chan *c, int order, gfp_t flags)
>   		struct ioat_descs *descs = &ioat_chan->descs[i];
>   
>   		descs->virt = dma_alloc_coherent(to_dev(ioat_chan),
> -						 SZ_2M, &descs->hw, flags);
> +					IOAT_CHUNK_SIZE, &descs->hw, flags);
>   		if (!descs->virt) {
>   			int idx;
>   
> 
> base-commit: ba4f184e126b751d1bffad5897f263108befc780
>