Re: Address mapping for vIOMMU

[Jason Wang]

On Thu, Mar 24, 2022 at 12:15 PM leohou <leohou163@163.com> wrote:
>
> hi all,
> When I use DPDK in guestOS  and  configering the VM with vIOMMU, I found that 
>  sending the gVA to the hardware device , the hardware device can't  find the 
> real data.
> But sending the gPA to the hardware device, the hardware device can  find the 
> real data.
>
> Environment:
> OS: Linux version 5.4.0-104-generic (buildd@ubuntu) (gcc version 9.3.0 
> (Ubuntu 9.3.0-17ubuntu1~20.04)) #118-Ubuntu SMP Wed Mar 2 19:02:41 UTC 2022
> QEMU: QEMU emulator version 4.2.1 (Debian 1:4.2-3ubuntu6.21)
> Device: virtio-net
>
> Question:
> The vIOMMU doesn't work?
> I know virtio-net does not have DMA, so when virtio-net and DPDK are 
> combined, IOMMU is not needed?

vIOMMU + virtio-net works for me like a charm.

DPDK supported vIOMMU long ago with virtio-net.

Make sure you vIOMMU is enabled in the guest (intel_iommu=on in guest
kernel command line, and enable_unsafe_noiommu_mode is *not* 1)

Thanks

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