Re: [PULL 08/34] hw/arm/virt: Let the virtio-iommu bypass MSIs

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Eric,

On 3/7/20 17:53, Peter Maydell wrote:
> From: Eric Auger <eric.auger@redhat.com>
> 
> At the moment the virtio-iommu translates MSI transactions.
> This behavior is inherited from ARM SMMU. The virt machine
> code knows where the guest MSI doorbells are so we can easily
> declare those regions as VIRTIO_IOMMU_RESV_MEM_T_MSI. With that
> setting the guest will not map MSIs through the IOMMU and those
> transactions will be simply bypassed.
> 
> Depending on which MSI controller is in use (ITS or GICV2M),
> we declare either:
> - the ITS interrupt translation space (ITS_base + 0x10000),
>    containing the GITS_TRANSLATOR or
> - The GICV2M single frame, containing the MSI_SETSP_NS register.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Message-id: 20200629070404.10969-6-eric.auger@redhat.com
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   include/hw/arm/virt.h |  7 +++++++
>   hw/arm/virt.c         | 30 ++++++++++++++++++++++++++++++
>   2 files changed, 37 insertions(+)


>   static void create_gic(VirtMachineState *vms)
> @@ -2198,8 +2200,36 @@ out:
>   static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>                                               DeviceState *dev, Error **errp)
>   {
> +    VirtMachineState *vms = VIRT_MACHINE(hotplug_dev);
> +
>       if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>           virt_memory_pre_plug(hotplug_dev, dev, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
> +        hwaddr db_start = 0, db_end = 0;
> +        char *resv_prop_str;
> +
> +        switch (vms->msi_controller) {
> +        case VIRT_MSI_CTRL_NONE:
> +            return;
> +        case VIRT_MSI_CTRL_ITS:
> +            /* GITS_TRANSLATER page */
> +            db_start = base_memmap[VIRT_GIC_ITS].base + 0x10000;
> +            db_end = base_memmap[VIRT_GIC_ITS].base +
> +                     base_memmap[VIRT_GIC_ITS].size - 1;
> +            break;
> +        case VIRT_MSI_CTRL_GICV2M:
> +            /* MSI_SETSPI_NS page */
> +            db_start = base_memmap[VIRT_GIC_V2M].base;
> +            db_end = db_start + base_memmap[VIRT_GIC_V2M].size - 1;
> +            break;
> +        }
> +        resv_prop_str = g_strdup_printf("0x%"PRIx64":0x%"PRIx64":%u",
> +                                        db_start, db_end,
> +                                        VIRTIO_IOMMU_RESV_MEM_T_MSI);
> +
> +        qdev_prop_set_uint32(dev, "len-reserved-regions", 1);

Where is "len-reserved-regions" declared?

Since qdev_prop_set_uint32() uses &error_abort, isn't this call
aborting the process? I am confused how this code path is exercised,
what am I missing?

> +        qdev_prop_set_string(dev, "reserved-regions[0]", resv_prop_str);
> +        g_free(resv_prop_str);
>       }
>   }
>