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Message-ID: <fffcf35b-0da5-4df5-9224-5ac4e28b5f3a@arm.com>
Date: Mon, 16 Oct 2023 12:58:47 +0100
From: Robin Murphy <robin.murphy@....com>
To: Christoph Hellwig <hch@....de>, Greg Ungerer <gerg@...ux-m68k.org>,
iommu@...ts.linux.dev
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Conor Dooley <conor@...nel.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Magnus Damm <magnus.damm@...il.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>, Wei Fang <wei.fang@....com>,
Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>,
NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org,
netdev@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-renesas-soc@...r.kernel.org, Jim Quinlan <james.quinlan@...adcom.com>
Subject: Re: [PATCH 07/12] dma-direct: simplify the use atomic pool logic in
dma_direct_alloc
On 16/10/2023 6:47 am, Christoph Hellwig wrote:
> The logic in dma_direct_alloc when to use the atomic pool vs remapping
> grew a bit unreadable. Consolidate it into a single check, and clean
> up the set_uncached vs remap logic a bit as well.
Reviewed-by: Robin Murphy <robin.murphy@....com>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> kernel/dma/direct.c | 25 ++++++++++---------------
> 1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index ec410af1d8a14e..1327d04fa32a25 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -234,27 +234,22 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_handle);
>
> /*
> - * Otherwise remap if the architecture is asking for it. But
> - * given that remapping memory is a blocking operation we'll
> - * instead have to dip into the atomic pools.
> + * Otherwise we require the architecture to either be able to
> + * mark arbitrary parts of the kernel direct mapping uncached,
> + * or remapped it uncached.
> */
> + set_uncached = IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED);
> remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
> - if (remap) {
> - if (dma_direct_use_pool(dev, gfp))
> - return dma_direct_alloc_from_pool(dev, size,
> - dma_handle, gfp);
> - } else {
> - if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
> - return NULL;
> - set_uncached = true;
> - }
> + if (!set_uncached && !remap)
> + return NULL;
> }
>
> /*
> - * Decrypting memory may block, so allocate the memory from the atomic
> - * pools if we can't block.
> + * Remapping or decrypting memory may block, allocate the memory from
> + * the atomic pools instead if we aren't allowed block.
> */
> - if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
> + if ((remap || force_dma_unencrypted(dev)) &&
> + dma_direct_use_pool(dev, gfp))
> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>
> /* we always manually zero the memory once we are done */
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