Re: [Qemu-devel] [PATCH for-4.2 v10 11/15] virtio-iommu: Expose the IOAPIC MSI reserved region when relevant

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jul 30, 2019 at 07:21:33PM +0200, Eric Auger wrote:
> We introduce a new msi_bypass field which indicates whether
> the IOAPIC MSI window [0xFEE00000 - 0xFEEFFFFF] must be exposed
> as a reserved region. By default the field is set to true at
> instantiation time. Later on we will introduce a property at
> virtio pci proxy level to turn it off.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> ---
> 
> v8 -> v9:
> - pass IOAPIC_RANGE_END to virtio_iommu_register_resv_region
> - take into account the change in the struct virtio_iommu_probe_resv_mem
>   definition
> - We just introduce the field here. A property will be introduced later on
>   at pci proxy level.
> ---
>  hw/virtio/virtio-iommu.c         | 36 ++++++++++++++++++++++++++++++++
>  include/hw/virtio/virtio-iommu.h |  1 +
>  2 files changed, 37 insertions(+)
> 
> diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
> index 66be9a4627..74038288b0 100644
> --- a/hw/virtio/virtio-iommu.c
> +++ b/hw/virtio/virtio-iommu.c
> @@ -39,6 +39,9 @@
>  #define VIOMMU_DEFAULT_QUEUE_SIZE 256
>  #define VIOMMU_PROBE_SIZE 512
>  
> +#define IOAPIC_RANGE_START      (0xfee00000)
> +#define IOAPIC_RANGE_END        (0xfeefffff)
> +
>  #define SUPPORTED_PROBE_PROPERTIES (\
>      1 << VIRTIO_IOMMU_PROBE_T_RESV_MEM)
>  

Sorry where are these numbers coming from?
Does this really work on all platforms?
With all guests?

> @@ -100,6 +103,30 @@ static void virtio_iommu_detach_endpoint_from_domain(viommu_endpoint *ep)
>      ep->domain = NULL;
>  }
>  
> +static void virtio_iommu_register_resv_region(viommu_endpoint *ep,
> +                                              uint8_t subtype,
> +                                              uint64_t start, uint64_t end)
> +{
> +    viommu_interval *interval;
> +    struct virtio_iommu_probe_resv_mem *resv_reg_prop;
> +    size_t prop_size = sizeof(struct virtio_iommu_probe_resv_mem);
> +    size_t value_size = prop_size -
> +                sizeof(struct virtio_iommu_probe_property);
> +
> +    interval = g_malloc0(sizeof(*interval));
> +    interval->low = start;
> +    interval->high = end;
> +
> +    resv_reg_prop = g_malloc0(prop_size);
> +    resv_reg_prop->head.type = VIRTIO_IOMMU_PROBE_T_RESV_MEM;
> +    resv_reg_prop->head.length = cpu_to_le64(value_size);
> +    resv_reg_prop->subtype = cpu_to_le64(subtype);
> +    resv_reg_prop->start = cpu_to_le64(start);
> +    resv_reg_prop->end = cpu_to_le64(end);
> +
> +    g_tree_insert(ep->reserved_regions, interval, resv_reg_prop);
> +}
> +
>  static viommu_endpoint *virtio_iommu_get_endpoint(VirtIOIOMMU *s,
>                                                    uint32_t ep_id)
>  {
> @@ -117,6 +144,12 @@ static viommu_endpoint *virtio_iommu_get_endpoint(VirtIOIOMMU *s,
>      ep->reserved_regions = g_tree_new_full((GCompareDataFunc)interval_cmp,
>                                              NULL, (GDestroyNotify)g_free,
>                                              (GDestroyNotify)g_free);
> +    if (s->msi_bypass) {
> +        virtio_iommu_register_resv_region(ep, VIRTIO_IOMMU_RESV_MEM_T_MSI,
> +                                          IOAPIC_RANGE_START,
> +                                          IOAPIC_RANGE_END);
> +    }
> +
>      return ep;
>  }
>  
> @@ -822,6 +855,9 @@ static void virtio_iommu_set_status(VirtIODevice *vdev, uint8_t status)
>  
>  static void virtio_iommu_instance_init(Object *obj)
>  {
> +    VirtIOIOMMU *s = VIRTIO_IOMMU(obj);
> +
> +    s->msi_bypass = true;
>  }
>  
>  static const VMStateDescription vmstate_virtio_iommu = {
> diff --git a/include/hw/virtio/virtio-iommu.h b/include/hw/virtio/virtio-iommu.h
> index f55f48d304..56c8b4e57f 100644
> --- a/include/hw/virtio/virtio-iommu.h
> +++ b/include/hw/virtio/virtio-iommu.h
> @@ -59,6 +59,7 @@ typedef struct VirtIOIOMMU {
>      GTree *domains;
>      QemuMutex mutex;
>      GTree *endpoints;
> +    bool msi_bypass;
>  } VirtIOIOMMU;
>  
>  #endif
> -- 
> 2.20.1