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Groups > linux.kernel > #1274862 > unrolled thread
| Started by | Marcel Apfelbaum <marcel.apfelbaum@gmail.com> |
|---|---|
| First post | 2015-11-22 14:10 +0100 |
| Last post | 2015-11-22 23:20 +0100 |
| Articles | 4 — 4 participants |
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Re: [PATCH v3 0/3] virtio DMA API core stuff Marcel Apfelbaum <marcel.apfelbaum@gmail.com> - 2015-11-22 14:10 +0100
Re: [PATCH v3 0/3] virtio DMA API core stuff David Woodhouse <dwmw2@infradead.org> - 2015-11-22 17:00 +0100
Re: [PATCH v3 0/3] virtio DMA API core stuff Marcel Apfelbaum <marcel@redhat.com> - 2015-11-22 18:10 +0100
Re: [PATCH v3 0/3] virtio DMA API core stuff "Michael S. Tsirkin" <mst@redhat.com> - 2015-11-22 23:20 +0100
| From | Marcel Apfelbaum <marcel.apfelbaum@gmail.com> |
|---|---|
| Date | 2015-11-22 14:10 +0100 |
| Subject | Re: [PATCH v3 0/3] virtio DMA API core stuff |
| Message-ID | <qxCyZ-4di-7@gated-at.bofh.it> |
On 11/08/2015 01:49 PM, Joerg Roedel wrote: > On Sun, Nov 08, 2015 at 12:37:47PM +0200, Michael S. Tsirkin wrote: >> I have no problem with that. For example, can we teach >> the DMA API on intel x86 to use PT for virtio by default? >> That would allow merging Andy's patches with >> full compatibility with old guests and hosts. > > Well, the only incompatibility comes from an experimental qemu feature, > more explicitly from a bug in that features implementation. So why > should we work around that in the kernel? I think it is not too hard to > fix qemu to generate a correct DMAR table which excludes the virtio > devices from iommu translation. Hi, I tried to generate a DMAR table that excludes some devices from IOMMU translation, however it does not help. The reason is, as far as I understand, that Linux kernel does not allow any device being outside an IOMMU scope if the iommu kernel option is activated. Does anybody know if it is "by design" or is simply an uncommon configuration? (some devices in an IOMMU scope, while others outside *any* IOMMU scope) Thanks, Marcel > > > Joerg > > _______________________________________________ > Virtualization mailing list > Virtualization@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | David Woodhouse <dwmw2@infradead.org> |
|---|---|
| Date | 2015-11-22 17:00 +0100 |
| Message-ID | <qxFdx-5OZ-19@gated-at.bofh.it> |
| In reply to | #1274862 |
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On Sun, 2015-11-22 at 15:06 +0200, Marcel Apfelbaum wrote: > > > I tried to generate a DMAR table that excludes some devices from > IOMMU translation, however it does not help. > > The reason is, as far as I understand, that Linux kernel does > not allow any device being outside an IOMMU scope if the > iommu kernel option is activated. > > Does anybody know if it is "by design" or is simply an uncommon > configuration? > (some devices in an IOMMU scope, while others outside *any* IOMMU > scope) That's a kernel bug in the way it handles per-device DMA operations. Or more to the point, in the way it doesn't — the non-translated devices end up being pointed to the intel_dma_ops despite the fact they shouldn't be. I'm working on that... -- dwmw2
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| From | Marcel Apfelbaum <marcel@redhat.com> |
|---|---|
| Date | 2015-11-22 18:10 +0100 |
| Message-ID | <qxGjg-6O6-7@gated-at.bofh.it> |
| In reply to | #1274892 |
On 11/22/2015 05:54 PM, David Woodhouse wrote: > On Sun, 2015-11-22 at 15:06 +0200, Marcel Apfelbaum wrote: >> >> >> I tried to generate a DMAR table that excludes some devices from >> IOMMU translation, however it does not help. >> >> The reason is, as far as I understand, that Linux kernel does >> not allow any device being outside an IOMMU scope if the >> iommu kernel option is activated. >> >> Does anybody know if it is "by design" or is simply an uncommon >> configuration? >> (some devices in an IOMMU scope, while others outside *any* IOMMU >> scope) > > That's a kernel bug in the way it handles per-device DMA operations. Or > more to the point, in the way it doesn't — the non-translated devices > end up being pointed to the intel_dma_ops despite the fact they > shouldn't be. I'm working on that... > Hi David, Thank you for the fast response. Sadly I am not familiar with the DMA/IOMMU code to contribute with a sane idea, but I'll gladly test it. If you lack the time and have an idea to share, I can give it a try though. Thanks, Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | "Michael S. Tsirkin" <mst@redhat.com> |
|---|---|
| Date | 2015-11-22 23:20 +0100 |
| Message-ID | <qxL9f-1sn-7@gated-at.bofh.it> |
| In reply to | #1274892 |
On Sun, Nov 22, 2015 at 03:54:21PM +0000, David Woodhouse wrote: > On Sun, 2015-11-22 at 15:06 +0200, Marcel Apfelbaum wrote: > > > > > > I tried to generate a DMAR table that excludes some devices from > > IOMMU translation, however it does not help. > > > > The reason is, as far as I understand, that Linux kernel does > > not allow any device being outside an IOMMU scope if the > > iommu kernel option is activated. > > > > Does anybody know if it is "by design" or is simply an uncommon > > configuration? > > (some devices in an IOMMU scope, while others outside *any* IOMMU > > scope) > > That's a kernel bug in the way it handles per-device DMA operations. Or > more to the point, in the way it doesn't — the non-translated devices > end up being pointed to the intel_dma_ops despite the fact they > shouldn't be. I'm working on that... > > -- > dwmw2 > Interesting. This seems to imply such configurations aren't common, so I wonder whether other guest OS-es treat them correctly. If many of them are, we probably shouldn't use this in QEMU: we care about guests actually working :) -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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