Re: [kvm-devel] [PATCH 1/8] KVM: PVDMA Host: Handle reqeusts for guest DMA mappings

Joerg Roedel
2007-11-12T15:58:01Z

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?

Joerg

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