Hi Stefano, Could you please answer, is swiotlb-xen driver designed to work on DomU kernel? http://marc.info/?l=linux-kernel&m=138269837007527&w=2 Thank you in advance. Regards, Andrii -- Andrii Tseglytskyi | Embedded Dev GlobalLogic www.globallogic.com _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote:> Hi Stefano, > > > Could you please answer, is swiotlb-xen driver designed to work on > DomU kernel?No. DomU device assignment will require an IOMMU I''m afraid.> http://marc.info/?l=linux-kernel&m=138269837007527&w=2 > > > > Thank you in advance. > > > Regards, > Andrii > > > -- > > Andrii Tseglytskyi | Embedded Dev > GlobalLogic > www.globallogic.com > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel
On Tue, 3 Dec 2013, Ian Campbell wrote:> On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote: > > Hi Stefano, > > > > > > Could you please answer, is swiotlb-xen driver designed to work on > > DomU kernel? > > No. DomU device assignment will require an IOMMU I''m afraid.The swiotlb-xen driver is designed to make DMA transactions safe in Dom0 as we don''t have IOMMU support in Xen yet.
Hi Ian, Thank you for your answer On Tue, Dec 3, 2013 at 4:18 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote:> On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote: >> Hi Stefano, >> >> >> Could you please answer, is swiotlb-xen driver designed to work on >> DomU kernel? > > No. DomU device assignment will require an IOMMU I''m afraid. >Do you mean IOMMU support in Xen? I found this as open item on the following page -> http://wiki.xenproject.org/wiki/Xen_ARM_TODO Regards, Andrii -- Andrii Tseglytskyi | Embedded Dev GlobalLogic www.globallogic.com
On Tue, 3 Dec 2013, Stefano Stabellini wrote:> On Tue, 3 Dec 2013, Ian Campbell wrote: > > On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote: > > > Hi Stefano, > > > > > > > > > Could you please answer, is swiotlb-xen driver designed to work on > > > DomU kernel? > > > > No. DomU device assignment will require an IOMMU I''m afraid. > > The swiotlb-xen driver is designed to make DMA transactions safe in Dom0 > as we don''t have IOMMU support in Xen yet.FYI you could modify it to run in a DomU without too much trouble, but I wouldn''t recommend it because: - you would still need to trust the DomU as much as you trust Dom0 because it could read/write all the RAM via DMA. At this point you loose most of the benefit of running the driver in a separate VM. - It would be slow because you would need to bounce all the DMA requests on the swiotlb buffer (this could be worked around with another 1:1 mapping, but at this point you loose even more flexibility, your DomU wouldn''t probably be able even to restart). So yes, it is only for Dom0 at the moment :-)
On Tue, 3 Dec 2013, Andrii Tseglytskyi wrote:> Hi Ian, > > Thank you for your answer > > On Tue, Dec 3, 2013 at 4:18 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote: > >> Hi Stefano, > >> > >> > >> Could you please answer, is swiotlb-xen driver designed to work on > >> DomU kernel? > > > > No. DomU device assignment will require an IOMMU I''m afraid. > > > > Do you mean IOMMU support in Xen? I found this as open item on the > following page -> http://wiki.xenproject.org/wiki/Xen_ARM_TODOYes, that''s right. IOMMU support in Xen would remove any needs for the swiotlb-xen in dom0 or any domU.
On Tue, 2013-12-03 at 16:28 +0200, Andrii Tseglytskyi wrote:> Hi Ian, > > Thank you for your answer > > On Tue, Dec 3, 2013 at 4:18 PM, Ian Campbell <Ian.Campbell@citrix.com> wrote: > > On Tue, 2013-12-03 at 16:11 +0200, Andrii Tseglytskyi wrote: > >> Hi Stefano, > >> > >> > >> Could you please answer, is swiotlb-xen driver designed to work on > >> DomU kernel? > > > > No. DomU device assignment will require an IOMMU I''m afraid. > > > > Do you mean IOMMU support in Xen?Yes> I found this as open item on the > following page -> http://wiki.xenproject.org/wiki/Xen_ARM_TODOCorrect. We do not yet support device passthrough. When it we do it will be with a requirement for an IOMMU. Ian.
>> > No. DomU device assignment will require an IOMMU I''m afraid. >> > >> >> Do you mean IOMMU support in Xen? I found this as open item on the >> following page -> http://wiki.xenproject.org/wiki/Xen_ARM_TODO > > Yes, that''s right. IOMMU support in Xen would remove any needs for the > swiotlb-xen in dom0 or any domU.OK got it. And it looks like there are no even draft implementations for Xen IOMMU, right? -- Andrii Tseglytskyi | Embedded Dev GlobalLogic www.globallogic.com
On Tue, 3 Dec 2013, Andrii Tseglytskyi wrote:> >> > No. DomU device assignment will require an IOMMU I''m afraid. > >> > > >> > >> Do you mean IOMMU support in Xen? I found this as open item on the > >> following page -> http://wiki.xenproject.org/wiki/Xen_ARM_TODO > > > > Yes, that''s right. IOMMU support in Xen would remove any needs for the > > swiotlb-xen in dom0 or any domU. > > OK got it. And it looks like there are no even draft implementations > for Xen IOMMU, right?correct