From: "Michael S. Tsirkin" <mst@redhat.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
linux-kernel@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
iommu@lists.linux.dev, Zelin Deng <zelin.deng@linux.alibaba.com>
Subject: Re: [RFC] dma-mapping: introduce dma_can_skip_unmap()
Date: Fri, 1 Mar 2024 06:50:05 -0500 [thread overview]
Message-ID: <20240301064632-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <64be2e23-c526-45d3-bb7b-29e31241bbef@arm.com>
On Fri, Mar 01, 2024 at 11:38:25AM +0000, Robin Murphy wrote:
> Not only is this idea not viable, the entire premise seems flawed - the
> reasons for virtio needing to use the DMA API at all are highly likely to be
> the same reasons for it needing to use the DMA API *properly* anyway.
The idea has nothing to do with virtio per se - we are likely not the
only driver that wastes a lot of memory (hot in cache, too) keeping DMA
addresses around for the sole purpose of calling DMA unmap. On a bunch
of systems unmap is always a nop and we could save some memory if there
was a way to find out. What is proposed is an API extension allowing
that for anyone - not just virtio.
--
MST
next prev parent reply other threads:[~2024-03-01 11:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-01 7:19 [RFC] dma-mapping: introduce dma_can_skip_unmap() Xuan Zhuo
2024-03-01 11:38 ` Robin Murphy
2024-03-01 11:50 ` Michael S. Tsirkin [this message]
2024-03-01 12:42 ` Robin Murphy
2024-03-01 13:41 ` Michael S. Tsirkin
2024-03-01 18:04 ` Robin Murphy
2024-03-02 9:58 ` Michael S. Tsirkin
2024-03-04 6:28 ` Xuan Zhuo
2024-03-04 6:19 ` Xuan Zhuo
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