From: Tom Murphy <tmurphy@arista.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>,
iommu@lists.linux-foundation.org,
Heiko Stuebner <heiko@sntech.de>,
Will Deacon <will.deacon@arm.com>,
David Brown <david.brown@linaro.org>,
Thierry Reding <thierry.reding@gmail.com>,
linux-s390@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
Krzysztof Kozlowski <krzk@kernel.org>,
Jonathan Hunter <jonathanh@nvidia.com>,
linux-rockchip@lists.infradead.org, Kukjin Kim <kgene@kernel.org>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
Andy Gross <andy.gross@linaro.org>,
linux-tegra@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Tom Murphy <murphyt7@tcd.ie>,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2 3/4] iommu/dma-iommu: Use the dev->coherent_dma_mask
Date: Mon, 6 May 2019 18:56:13 +0100 [thread overview]
Message-ID: <CAPL0++61WytVhs63tvt+hdpZKXGinrkYx=4nDtNx1UoNTRWWjw@mail.gmail.com> (raw)
In-Reply-To: <96ebb6fc-a889-fa94-09ba-65d505b85724@arm.com>
Just to make this clear, I won't apply Christoph's patch (the one in
this email thread) and instead the only change I will make is to
rename dma_limit to dma_mask.
On Tue, Apr 30, 2019 at 1:05 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 30/04/2019 12:32, Christoph Hellwig wrote:
> > On Tue, Apr 30, 2019 at 12:27:02PM +0100, Robin Murphy wrote:
> >>> Hmm, I don't think we need the DMA mask for the MSI mapping, this
> >>> should probably always use a 64-bit mask.
> >>
> >> If that were true then we wouldn't need DMA masks for regular mappings
> >> either. If we have to map the MSI doorbell at all, then we certainly have to
> >> place it at an IOVA that the relevant device is actually capable of
> >> addressing.
> >
> > Well, as shown by the patch below we don't even look at the DMA mask
> > for the MSI page - we just allocate from bottom to top.
>
> In the trivial cookie for unmanaged domains, yes, but in that case the
> responsibility is on VFIO to provide a suitable (i.e. sub-32-bit)
> address range for that cookie in the first place. In the managed case,
> allocation uses the streaming mask via iommu_dma_get_msi_page() calling
> __iommu_dma_map(). Admittedly the mask can then get overlooked when
> reusing an existing mapping, which strictly could pose a problem if you
> have multiple devices with incompatible masks in the same group (and
> such that the PCI stuff doesn't already mitigate it), but that's such an
> obscure corner case that I'm reticent to introduce the complication to
> handle it until it's actually proven necessary.
>
> Robin.
next prev parent reply other threads:[~2019-05-06 17:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-30 0:29 [PATCH v2 0/4] iommu/amd: Convert the AMD iommu driver to the dma-iommu api Tom Murphy
2019-04-30 0:29 ` [PATCH v2 1/4] iommu: Add gfp parameter to iommu_ops::map Tom Murphy
2019-04-30 0:29 ` [PATCH v2 2/4] iommu/dma-iommu: Handle deferred devices Tom Murphy
2019-04-30 13:42 ` Robin Murphy
2019-04-30 14:04 ` Tom Murphy
2019-04-30 0:29 ` [PATCH v2 3/4] iommu/dma-iommu: Use the dev->coherent_dma_mask Tom Murphy
2019-04-30 11:12 ` Christoph Hellwig
2019-04-30 11:27 ` Robin Murphy
2019-04-30 11:32 ` Christoph Hellwig
2019-04-30 12:04 ` Robin Murphy
2019-05-06 17:56 ` Tom Murphy [this message]
2019-05-07 6:35 ` Christoph Hellwig
2019-04-30 0:29 ` [PATCH v2 4/4] iommu/amd: Convert the AMD iommu driver to the dma-iommu api Tom Murphy
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