From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, robh@kernel.org, aik@ozlabs.ru,
jasowang@redhat.com, joe@perches.com,
linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net,
david@gibson.dropbear.id.au
Subject: Re: [RFC] virtio: Use DMA MAP API for devices without an IOMMU
Date: Fri, 06 Apr 2018 07:18:33 +1000 [thread overview]
Message-ID: <1522963113.21446.211.camel@kernel.crashing.org> (raw)
In-Reply-To: <20180405213042-mutt-send-email-mst@kernel.org>
On Thu, 2018-04-05 at 21:34 +0300, Michael S. Tsirkin wrote:
> > In this specific case, because that would make qemu expect an iommu,
> > and there isn't one.
>
>
> I think that you can set iommu_platform in qemu without an iommu.
No I mean the platform has one but it's not desirable for it to be used
due to the performance hit.
Cheers,
Ben.
>
> > Anshuman, you need to provide more background here. I don't have time
> > right now it's late, but explain about the fact that this is for a
> > specific type of secure VM which has only a limited pool of (insecure)
> > memory that can be shared with qemu, so all IOs need to bounce via that
> > pool, which can be achieved by using swiotlb.
> >
> > Note: this isn't urgent, we can discuss alternative approaches, this is
> > just to start the conversation.
> >
> > Cheers,
> > Ben.
next prev parent reply other threads:[~2018-04-05 21:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-05 10:56 [RFC] virtio: Use DMA MAP API for devices without an IOMMU Anshuman Khandual
2018-04-05 11:14 ` Balbir Singh
2018-04-05 11:28 ` Anshuman Khandual
2018-04-05 14:39 ` Anshuman Khandual
2018-04-05 14:54 ` Michael S. Tsirkin
2018-04-05 15:09 ` Benjamin Herrenschmidt
2018-04-05 18:34 ` Michael S. Tsirkin
2018-04-05 21:18 ` Benjamin Herrenschmidt [this message]
2018-04-06 2:53 ` Anshuman Khandual
2018-04-06 7:16 ` Christoph Hellwig
2018-04-06 8:37 ` Benjamin Herrenschmidt
2018-04-15 12:11 ` Christoph Hellwig
2018-04-18 3:17 ` Anshuman Khandual
2018-04-18 16:20 ` Michael S. Tsirkin
2018-05-01 16:34 ` Ram Pai
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