On Monday 12 November 2007 21:25:22 Joerg Roedel wrote:
> On Wed, Nov 07, 2007 at 04:21:02PM +0200, Amit Shah wrote:
> > @@ -1649,6 +1913,15 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
> >     }
> >
> >     switch (nr) {
> > +   case KVM_PV_DMA_MAP:
> > +           ret = pv_map_hypercall(vcpu, a0, a1);
> > +           break;
> > +   case KVM_PV_DMA_UNMAP:
> > +           ret = pv_unmap_hypercall(vcpu, a0);
> > +           break;
> > +   case KVM_PV_PCI_DEVICE:
> > +           ret = pv_mapped_pci_device_hypercall(vcpu, a0);
> > +           break;
> >     default:
> >             ret = -KVM_ENOSYS;
> >             break;
>
> How does synchronization work with that design? I don't see a hypercall
> to synchronize de DMA buffers. It will only work if GART is used as the
> dma_ops backend on the host side and not with SWIOTLB. But GART can be
> configured away.  Or do I miss something?

A per-VM lock is needed while mapping or unmapping. It's one of the TODOs.
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