Re: [PATCH v3 0/3] virtio DMA API core stuff

From: David Woodhouse <dwmw2@infradead.org>
To: marcel@redhat.com, Joerg Roedel <jroedel@suse.de>,
	"Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>,
	KVM <kvm@vger.kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Sebastian Ott <sebott@linux.vnet.ibm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Andy Lutomirski <luto@kernel.org>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Linux Virtualization <virtualization@lists.linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff
Date: Sun, 22 Nov 2015 15:54:21 +0000	[thread overview]
Message-ID: <1448207661.89124.50.camel@infradead.org> (raw)
In-Reply-To: <5651BDC0.2040206@gmail.com>

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On Sun, 2015-11-22 at 15:06 +0200, Marcel Apfelbaum wrote:
> 
> 
> I tried to generate a DMAR table that excludes some devices from
> IOMMU translation, however it does not help.
> 
> The reason is, as far as I understand, that Linux kernel does
> not allow any device being outside an IOMMU scope if the
> iommu kernel option is activated.
> 
> Does anybody know if it is "by design" or is simply an uncommon
> configuration?
> (some devices in an IOMMU scope, while others outside *any* IOMMU
> scope)

That's a kernel bug in the way it handles per-device DMA operations. Or
more to the point, in the way it doesn't — the non-translated devices
end up being pointed to the intel_dma_ops despite the fact they
shouldn't be. I'm working on that...

-- 
dwmw2

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