From: Joerg Roedel <joro@8bytes.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: per-device dma_map_ops for intel-iommu?
Date: Thu, 11 Apr 2019 15:57:49 +0200 [thread overview]
Message-ID: <20190411135749.GE4518@8bytes.org> (raw)
In-Reply-To: <b491bb987c8cc3f95328d33586ec25c497cc8b8b.camel@infradead.org>
On Tue, Apr 09, 2019 at 05:03:52PM +0300, David Woodhouse wrote:
> On Tue, 2019-04-09 at 15:59 +0200, Christoph Hellwig wrote:
> > Hi David and Joerg,
> >
> > do you remember a good reason why intel-iommu is not using per-device
> > dma_map_ops like the AMD iommu or the various ARM iommus?
> >
> > Right now intel-iommu.c contains a half-asses reimplementation of the
> > dma direct code for the iommu_no_mapping() case, and it would seem
> > much nicer to just fall back to that case and not even call into
> > intel-iommu in that case.
>
> Other than the complexities about passthrough mode and various "oh shit
> we forgot to actually test that iommu+gfx actually works before
> shipping hardware" type of quirks that bypass the IOMMU for certain
> devices — and retpolines, which I think you already dealt with — no, no
> good reason that I recall.
Same here, I looked into this in the past as well, but I can't recall
any reason this was left in place.
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: iommu@lists.linux-foundation.org, Christoph Hellwig <hch@lst.de>,
linux-kernel@vger.kernel.org
Subject: Re: per-device dma_map_ops for intel-iommu?
Date: Thu, 11 Apr 2019 15:57:49 +0200 [thread overview]
Message-ID: <20190411135749.GE4518@8bytes.org> (raw)
Message-ID: <20190411135749.aDzRA1NFU8IEnkFu_qQrLYDDrVa2MQ2SRCgAo5DWiKQ@z> (raw)
In-Reply-To: <b491bb987c8cc3f95328d33586ec25c497cc8b8b.camel@infradead.org>
On Tue, Apr 09, 2019 at 05:03:52PM +0300, David Woodhouse wrote:
> On Tue, 2019-04-09 at 15:59 +0200, Christoph Hellwig wrote:
> > Hi David and Joerg,
> >
> > do you remember a good reason why intel-iommu is not using per-device
> > dma_map_ops like the AMD iommu or the various ARM iommus?
> >
> > Right now intel-iommu.c contains a half-asses reimplementation of the
> > dma direct code for the iommu_no_mapping() case, and it would seem
> > much nicer to just fall back to that case and not even call into
> > intel-iommu in that case.
>
> Other than the complexities about passthrough mode and various "oh shit
> we forgot to actually test that iommu+gfx actually works before
> shipping hardware" type of quirks that bypass the IOMMU for certain
> devices — and retpolines, which I think you already dealt with — no, no
> good reason that I recall.
Same here, I looked into this in the past as well, but I can't recall
any reason this was left in place.
Joerg
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next prev parent reply other threads:[~2019-04-11 13:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-09 13:59 per-device dma_map_ops for intel-iommu? Christoph Hellwig
2019-04-09 13:59 ` Christoph Hellwig
[not found] ` <20190409135924.GA11431-jcswGhMUV9g@public.gmane.org>
2019-04-09 14:03 ` David Woodhouse
2019-04-09 14:03 ` David Woodhouse
2019-04-09 14:03 ` David Woodhouse
2019-04-11 13:57 ` Joerg Roedel [this message]
2019-04-11 13:57 ` Joerg Roedel
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