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

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

On Mon, Sep 06, 2021 at 04:57:39PM +0200, Eric Auger wrote:
> 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.

Those are handled by x86_iommu_set_default() and
pc_machine_device_plug_cb() (below) respectively. I considered factoring
it but I think it just adds complexity.

Thanks,
Jean

> 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
>