linux-kernel - Re: [PATCH v5 00/10] virtio DMA API, yet again

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Date:	Fri, 29 Jan 2016 11:01:00 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Andy Lutomirski <luto@...nel.org>,
	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org, Joerg Roedel <jroedel@...e.de>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Christoph Hellwig <hch@....de>, KVM <kvm@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	David Vrabel <david.vrabel@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v5 00/10] virtio DMA API, yet again

On Thu, 2016-01-28 at 18:31 -0800, Andy Lutomirski wrote:
> 
> To everyone else: we've waffled on this for way too long.  I think
> we should to get DMA API implementation in with a conservative
> policy like this rather than waiting until we achieve perfection.
> I'm tired of carrying these patches around.

Yeah, do it.

However,,, shouldn't the generic no-op DMA ops be checking the dma_mask
of the device and bitching if it can't reach the address in question?

Also, wasn't Christoph looking at making per-device DMA ops more
generic instead of an 'archdata' thing on basically every platform? Or
did I just imagine that part?

Not that I'm suggesting you make the s390 patch wait for that *instead*
of using archdata there, mind you. But I was kind of planning to let
the dust settle on this lot before I sort out the theoretical-except-
in-simulation issues with VT-d IOMMU covering *some* devices but not
all.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation


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