From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"Michael S. Tsirkin" <mst@redhat.com>
Cc: robh@kernel.org, aik@ozlabs.ru, jasowang@redhat.com,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, joe@perches.com,
david@gibson.dropbear.id.au, linuxppc-dev@lists.ozlabs.org,
elfring@users.sourceforge.net
Subject: Re: [RFC] virtio: Use DMA MAP API for devices without an IOMMU
Date: Fri, 6 Apr 2018 08:23:10 +0530 [thread overview]
Message-ID: <70cb433f-a8f7-5199-3c96-a760c7624804@linux.vnet.ibm.com> (raw)
In-Reply-To: <1522963113.21446.211.camel@kernel.crashing.org>
On 04/06/2018 02:48 AM, Benjamin Herrenschmidt wrote:
> 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.
Also the only requirement is to bounce the I/O buffers through SWIOTLB
implemented as DMA API which the virtio core understands. There is no
need for an IOMMU to be involved for the device representation in this
case IMHO.
next prev parent reply other threads:[~2018-04-06 2:53 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
2018-04-06 2:53 ` Anshuman Khandual [this message]
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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