From: David Woodhouse <dwmw2@infradead.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
Andy Lutomirski <luto@kernel.org>,
linux-kernel@vger.kernel.org, Joerg Roedel <jroedel@suse.de>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
Sebastian Ott <sebott@linux.vnet.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Christoph Hellwig <hch@lst.de>,
benh@kernel.crashing.org, KVM <kvm@vger.kernel.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
linux-s390 <linux-s390@vger.kernel.org>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff
Date: Wed, 28 Oct 2015 22:35:27 +0900 [thread overview]
Message-ID: <1446039327.3405.216.camel@infradead.org> (raw)
In-Reply-To: <20151028132331-mutt-send-email-mst@redhat.com>
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On Wed, 2015-10-28 at 13:35 +0200, Michael S. Tsirkin wrote:
> E.g. on intel x86, there's an option iommu=pt which does the 1:1
> thing for devices when used by kernel, but enables
> the iommu if used by userspace/VMs.
That's none of your business.
You call the DMA API when you do DMA. That's all there is to it.
If the IOMMU happens to be in passthrough mode, or your device happens
to not to be routed through an IOMMU today, then I/O virtual address
you get back from the DMA API will look a *lot* like the physical
address you asked the DMA to map. You might think there's no IOMMU. We
couldn't possibly comment.
Use the DMA API. Always. Let the platform worry about whether it
actually needs to *do* anything or not.
--
dwmw2
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WARNING: multiple messages have this Message-ID (diff)
From: David Woodhouse <dwmw2@infradead.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-s390 <linux-s390@vger.kernel.org>,
Joerg Roedel <jroedel@suse.de>, KVM <kvm@vger.kernel.org>,
benh@kernel.crashing.org,
Sebastian Ott <sebott@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Christian Borntraeger <borntraeger@de.ibm.com>,
Andy Lutomirski <luto@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Christoph Hellwig <hch@lst.de>,
Martin Schwidefsky <schwidefsky@de.ibm.com>
Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff
Date: Wed, 28 Oct 2015 22:35:27 +0900 [thread overview]
Message-ID: <1446039327.3405.216.camel@infradead.org> (raw)
In-Reply-To: <20151028132331-mutt-send-email-mst@redhat.com>
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On Wed, 2015-10-28 at 13:35 +0200, Michael S. Tsirkin wrote:
> E.g. on intel x86, there's an option iommu=pt which does the 1:1
> thing for devices when used by kernel, but enables
> the iommu if used by userspace/VMs.
That's none of your business.
You call the DMA API when you do DMA. That's all there is to it.
If the IOMMU happens to be in passthrough mode, or your device happens
to not to be routed through an IOMMU today, then I/O virtual address
you get back from the DMA API will look a *lot* like the physical
address you asked the DMA to map. You might think there's no IOMMU. We
couldn't possibly comment.
Use the DMA API. Always. Let the platform worry about whether it
actually needs to *do* anything or not.
--
dwmw2
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next prev parent reply other threads:[~2015-10-28 13:35 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-28 6:38 [PATCH v3 0/3] virtio DMA API core stuff Andy Lutomirski
2015-10-28 6:38 ` [PATCH v3 1/3] virtio_net: Stop doing DMA from the stack Andy Lutomirski
2015-10-28 7:08 ` Michael S. Tsirkin
2015-10-28 7:08 ` Michael S. Tsirkin
2015-10-28 6:38 ` Andy Lutomirski
2015-10-28 6:38 ` [PATCH v3 2/3] virtio_ring: Support DMA APIs Andy Lutomirski
2015-10-28 6:38 ` Andy Lutomirski
2015-10-28 6:39 ` [PATCH v3 3/3] virtio_pci: Use the DMA API Andy Lutomirski
2015-10-28 6:39 ` Andy Lutomirski
2015-10-28 6:53 ` [PATCH v3 0/3] virtio DMA API core stuff David Woodhouse
2015-10-28 6:53 ` David Woodhouse
2015-10-28 7:09 ` Andy Lutomirski
2015-10-28 7:09 ` Andy Lutomirski
2015-10-28 7:17 ` Michael S. Tsirkin
2015-10-28 7:17 ` Michael S. Tsirkin
2015-10-28 7:40 ` Christian Borntraeger
2015-10-28 7:40 ` Christian Borntraeger
2015-10-28 8:09 ` David Woodhouse
2015-10-28 8:09 ` David Woodhouse
2015-10-28 11:35 ` Michael S. Tsirkin
2015-10-28 11:35 ` Michael S. Tsirkin
2015-10-28 13:35 ` David Woodhouse [this message]
2015-10-28 13:35 ` David Woodhouse
2015-10-28 14:05 ` Michael S. Tsirkin
2015-10-28 14:05 ` Michael S. Tsirkin
2015-10-28 14:13 ` David Woodhouse
2015-10-28 14:13 ` David Woodhouse
2015-10-28 14:22 ` Michael S. Tsirkin
2015-10-28 14:22 ` Michael S. Tsirkin
2015-10-28 14:32 ` David Woodhouse
2015-10-28 14:32 ` David Woodhouse
2015-10-28 16:12 ` Michael S. Tsirkin
2015-10-28 22:51 ` Andy Lutomirski
2015-10-28 22:51 ` Andy Lutomirski
2015-10-29 9:01 ` Michael S. Tsirkin
2015-10-29 9:01 ` Michael S. Tsirkin
2015-10-29 16:18 ` David Woodhouse
2015-10-29 16:18 ` David Woodhouse
2015-11-08 10:37 ` Michael S. Tsirkin
2015-11-08 10:37 ` Michael S. Tsirkin
2015-11-08 11:49 ` Joerg Roedel
2015-11-08 11:49 ` Joerg Roedel
2015-11-10 15:02 ` Michael S. Tsirkin
2015-11-10 15:02 ` Michael S. Tsirkin
2015-11-10 18:54 ` Andy Lutomirski
2015-11-10 18:54 ` Andy Lutomirski
2015-11-11 10:05 ` Michael S. Tsirkin
2015-11-11 10:05 ` Michael S. Tsirkin
2015-11-11 15:56 ` Andy Lutomirski
2015-11-11 22:30 ` David Woodhouse
2015-11-11 22:30 ` David Woodhouse
2015-11-12 11:09 ` Michael S. Tsirkin
2015-11-12 11:09 ` Michael S. Tsirkin
2015-11-12 12:18 ` David Woodhouse
2015-11-12 12:18 ` David Woodhouse
2015-11-11 15:56 ` Andy Lutomirski
2015-11-22 13:06 ` Marcel Apfelbaum
2015-11-22 13:06 ` Marcel Apfelbaum
2015-11-22 15:54 ` David Woodhouse
2015-11-22 15:54 ` David Woodhouse
2015-11-22 17:04 ` Marcel Apfelbaum
2015-11-22 17:04 ` Marcel Apfelbaum
2015-11-22 22:11 ` Michael S. Tsirkin
2015-11-22 22:11 ` Michael S. Tsirkin
2015-11-08 12:00 ` David Woodhouse
2015-11-08 12:00 ` David Woodhouse
2015-10-30 15:16 ` Joerg Roedel
2015-10-30 15:16 ` Joerg Roedel
2015-11-11 9:11 ` Michael S. Tsirkin
2015-11-11 9:11 ` Michael S. Tsirkin
2015-10-30 16:54 ` David Woodhouse
2015-10-30 16:54 ` David Woodhouse
2015-11-03 10:24 ` Paolo Bonzini
2015-11-03 10:24 ` Paolo Bonzini
2015-10-28 16:12 ` Michael S. Tsirkin
2015-10-28 8:36 ` Benjamin Herrenschmidt
2015-10-28 8:36 ` Benjamin Herrenschmidt
2015-10-28 11:23 ` Michael S. Tsirkin
2015-10-28 11:23 ` Michael S. Tsirkin
2015-10-28 13:37 ` David Woodhouse
2015-10-28 13:37 ` David Woodhouse
2015-10-28 14:07 ` Michael S. Tsirkin
2015-10-28 14:07 ` Michael S. Tsirkin
2015-11-19 13:45 ` Michael S. Tsirkin
2015-11-19 13:45 ` Michael S. Tsirkin
2015-11-19 21:59 ` Andy Lutomirski
2015-11-19 21:59 ` Andy Lutomirski
2015-11-19 23:38 ` David Woodhouse
2015-11-19 23:38 ` David Woodhouse
2015-11-20 2:56 ` Benjamin Herrenschmidt
2015-11-20 2:56 ` Benjamin Herrenschmidt
2015-11-20 8:34 ` Michael S. Tsirkin
2015-11-20 8:34 ` Michael S. Tsirkin
2015-11-20 8:21 ` Michael S. Tsirkin
2015-11-20 8:21 ` Michael S. Tsirkin
2015-11-22 15:58 ` David Woodhouse
2015-11-22 15:58 ` David Woodhouse
2015-11-22 21:52 ` Michael S. Tsirkin
2015-11-22 21:52 ` Michael S. Tsirkin
2015-11-22 22:21 ` David Woodhouse
2015-11-22 22:21 ` David Woodhouse
2015-11-23 7:56 ` Michael S. Tsirkin
2015-11-23 7:56 ` Michael S. Tsirkin
2015-11-22 22:21 ` David Woodhouse
2015-11-22 22:21 ` David Woodhouse
2015-11-20 6:56 ` Michael S. Tsirkin
2015-11-20 6:56 ` Michael S. Tsirkin
2015-11-20 7:47 ` Michael S. Tsirkin
2015-11-20 7:47 ` Michael S. Tsirkin
-- strict thread matches above, loose matches on Subject: below --
2015-10-28 6:38 Andy Lutomirski
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