From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
linux-doc@vger.kernel.org, iommu@lists.linux.dev
Subject: Re: [PATCH] dma: DMA_ATTR_SKIP_CPU_SYNC documentation tweaks
Date: Thu, 20 Jul 2023 08:07:42 +0200 [thread overview]
Message-ID: <20230720060742.GA2987@lst.de> (raw)
In-Reply-To: <98ef4f76d7a5f90b0878e649a70b101402b8889d.1689761699.git.mst@redhat.com>
On Wed, Jul 19, 2023 at 06:15:59AM -0400, Michael S. Tsirkin wrote:
> A recent patchset highlighted to me that DMA_ATTR_SKIP_CPU_SYNC
> might be easily misunderstood.
.. just curious: what patchset is that? DMA_ATTR_SKIP_CPU_SYNC is
often a bad idea and all users probably could use a really good
audit..
> #define DMA_ATTR_NO_KERNEL_MAPPING (1UL << 4)
> /*
> - * DMA_ATTR_SKIP_CPU_SYNC: Allows platform code to skip synchronization of
> - * the CPU cache for the given buffer assuming that it has been already
> - * transferred to 'device' domain.
> + * DMA_ATTR_SKIP_CPU_SYNC: Allows platform code to skip synchronization of the
> + * CPU and device domains for the given buffer.
While we're at it, I think "allows" is the wrong word here, we really
must skip the synchronization or else we're in trouble.
next prev parent reply other threads:[~2023-07-20 6:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-19 10:15 [PATCH] dma: DMA_ATTR_SKIP_CPU_SYNC documentation tweaks Michael S. Tsirkin
2023-07-20 6:07 ` Christoph Hellwig [this message]
2023-07-20 6:21 ` Michael S. Tsirkin
2023-07-20 6:25 ` Christoph Hellwig
2023-07-20 6:30 ` Michael S. Tsirkin
2023-07-20 6:34 ` Michael S. Tsirkin
2023-07-20 6:43 ` Christoph Hellwig
2023-07-20 7:06 ` Michael S. Tsirkin
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