Re: [PATCH v2 7/8] pc: Allow instantiating a virtio-iommu device

[Eric Auger]

Hi Jean,

On 9/3/21 4:32 PM, Jean-Philippe Brucker wrote:
> From: Eric Auger <eric.auger@redhat.com>
>
> Add a hotplug handler for virtio-iommu on x86 and set the necessary
> reserved region property. On x86, the [0xfee00000, 0xfeefffff] DMA
> region is reserved for MSIs. DMA transactions to this range either
> trigger IRQ remapping in the IOMMU or bypasses IOMMU translation.
s/bypasses/bypass.
> Although virtio-iommu does not support IRQ remapping it must be informed
> of the reserved region so that it can forward DMA transactions targeting
> this region.

>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
Feel free to remove my SoB. I have done much here.
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  hw/i386/pc.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 694fc9ce07..c1e1cffe16 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -797,6 +797,11 @@ void pc_machine_done(Notifier *notifier, void *data)
>                       "irqchip support.");
>          exit(EXIT_FAILURE);
>      }
> +
> +    if (pcms->virtio_iommu && x86_iommu_get_default()) {
> +        error_report("QEMU does not support multiple vIOMMUs for x86 yet.");
> +        exit(EXIT_FAILURE);
> +    }
>  }

I think you shall detect the case of dual instantiation of intel_iommu
and virtio-iommu. Maybe pc_hotplug_allowed() can be used for that. Note
that both devices can be refered to in either order.
>  
>  void pc_guest_info_init(PCMachineState *pcms)
> @@ -1376,6 +1381,14 @@ static void 
> pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
>                 object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI)) {
>          pc_virtio_md_pci_pre_plug(hotplug_dev, dev, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
> +        /* Declare the reserved MSI region */
> +        char *resv_prop_str = g_strdup_printf("0xfee00000:0xfeefffff:%d",
> +                                              VIRTIO_IOMMU_RESV_MEM_T_MSI);
> +
> +        qdev_prop_set_uint32(dev, "len-reserved-regions", 1);
> +        qdev_prop_set_string(dev, "reserved-regions[0]", resv_prop_str);
> +        g_free(resv_prop_str);
>      }
>  }
>  
> @@ -1393,6 +1406,11 @@ static void pc_machine_device_plug_cb(HotplugHandler 
> *hotplug_dev,
>          PCMachineState *pcms = PC_MACHINE(hotplug_dev);
>          PCIDevice *pdev = PCI_DEVICE(dev);
>  
> +        if (pcms->virtio_iommu) {
> +            error_setg(errp,
> +                       "QEMU does not support multiple vIOMMUs for x86 
> yet.");
> +            return;
> +        }
>          pcms->virtio_iommu = true;
>          pcms->virtio_iommu_bdf = pci_get_bdf(pdev);
>      }
> @@ -1436,7 +1454,8 @@ static HotplugHandler 
> *pc_get_hotplug_handler(MachineState *machine,
>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) ||
>          object_dynamic_cast(OBJECT(dev), TYPE_CPU) ||
>          object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_PMEM_PCI) ||
> -        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI)) {
> +        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MEM_PCI) ||
> +        object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
>          return HOTPLUG_HANDLER(machine);
>      }
>  
Thanks

Eric