Re: [PATCH v4 0/6] virtio core DMA API conversion

On 09/11/2015 13:15, Michael S. Tsirkin wrote: > Well that's not exactly true. I think we would like to make > it possible to put virtio devices behind an IOMMU on x86, > but if this means existing guests break, then many people won't be able > to use this option: having to find out which kernel

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Thu, Oct 29, 2015 at 06:09:45PM -0700, Andy Lutomirski wrote: > This switches virtio to use the DMA API unconditionally. I'm sure > it breaks things, but it seems to work on x86 using virtio-pci, with > and without Xen, and using both the modern 1.0 variant and the > legacy variant. > > This

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, 2015-11-09 at 18:18 -0800, Andy Lutomirski wrote: > > /* Qumranet donated their vendor ID for devices 0x1000 thru 0x10FF. > */ > static const struct pci_device_id virtio_pci_id_table[] = { >     { PCI_DEVICE(0x1af4, PCI_ANY_ID) }, >     { 0 } > }; > > Can we match on that range?

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, 2015-11-09 at 16:46 -0800, Andy Lutomirski wrote: > The problem here is that in some of the problematic cases the virtio > driver may not even be loaded.  If someone runs an L1 guest with an > IOMMU-bypassing virtio device and assigns it to L2 using vfio, then > *boom* L1 crashes.  (Same

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, 2015-11-09 at 18:18 -0800, Andy Lutomirski wrote: > > Which leaves the special case of Xen, where even preexisting devices > don't bypass the IOMMU.  Can we keep this specific to powerpc and > sparc?  On x86, this problem is basically nonexistent, since the IOMMU > is properly

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, Nov 9, 2015 at 9:28 PM, Benjamin Herrenschmidt wrote: > On Mon, 2015-11-09 at 18:18 -0800, Andy Lutomirski wrote: >> >> /* Qumranet donated their vendor ID for devices 0x1000 thru 0x10FF. >> */ >> static const struct pci_device_id virtio_pci_id_table[] = { >>

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, Nov 9, 2015 at 9:26 PM, Benjamin Herrenschmidt wrote: > On Mon, 2015-11-09 at 18:18 -0800, Andy Lutomirski wrote: >> >> Which leaves the special case of Xen, where even preexisting devices >> don't bypass the IOMMU. Can we keep this specific to powerpc and >>

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, Nov 9, 2015 at 6:04 PM, Benjamin Herrenschmidt wrote: > On Mon, 2015-11-09 at 16:46 -0800, Andy Lutomirski wrote: >> The problem here is that in some of the problematic cases the virtio >> driver may not even be loaded. If someone runs an L1 guest with an >>

Re: [PATCH v4 0/6] virtio core DMA API conversion

On 2015-11-10 03:18, Andy Lutomirski wrote: > On Mon, Nov 9, 2015 at 6:04 PM, Benjamin Herrenschmidt >> I thus go back to my original statement, it's a LOT easier to handle if >> the device itself is self describing, indicating whether it is set to >> bypass a host iommu or not. For L1->L2, well,

Re: [PATCH v4 0/6] virtio core DMA API conversion

So ... I've finally tried to sort that out for powerpc and I can't find a way to make that work that isn't a complete pile of stinking shit. I'm very tempted to go back to my original idea: virtio itself should indicate it's "bypassing ability" via the virtio config space or some other bit (like

Re: [PATCH v4 0/6] virtio core DMA API conversion

On Mon, Nov 9, 2015 at 2:58 PM, Benjamin Herrenschmidt wrote: > So ... > > I've finally tried to sort that out for powerpc and I can't find a way > to make that work that isn't a complete pile of stinking shit. > > I'm very tempted to go back to my original idea: virtio