Re: [PATCH v3 3/3] hw: Set virtio-iommu aw-bits default value on pc_q35 and arm virt

[Cédric Le Goater]

On 2/8/24 11:10, Eric Auger wrote:

Currently the default input range can extend to 64 bits. On x86,
when the virtio-iommu protects vfio devices, the physical iommu
may support only 39 bits. Let's set the default to 39, as done
for the intel-iommu. On ARM we set 48b as a default (matching
SMMUv3 SMMU_IDR5.VAX == 0).

We use hw_compat_8_2 to handle the compatibility for machines
before 9.0 which used to have a virtio-iommu default input range
of 64 bits.

Of course if aw-bits is set from the command line, the default
is overriden.

Signed-off-by: Eric Auger <eric.au...@redhat.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
Tested-by: Yanghang Liu<yangh...@redhat.com>

Reviewed-by: Cédric Le Goater <c...@redhat.com>

Thanks,

C.

---

v2 -> v3:
- collected Zhenzhong's R-b
- use &error_abort instead of NULL error handle
   on object_property_get_uint() call (Cédric)
- use VTD_HOST_AW_39BIT (Cédric)

v1 -> v2:
- set aw-bits to 48b on ARM
- use hw_compat_8_2 to handle the compat for older machines
   which used 64b as a default
---
  hw/arm/virt.c            | 6 ++++++
  hw/core/machine.c        | 5 ++++-
  hw/i386/pc.c             | 6 ++++++
  hw/virtio/virtio-iommu.c | 2 +-
  4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 368c2a415a..0994f2a560 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -2716,10 +2716,16 @@ static void 
virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MD_PCI)) {
          virtio_md_pci_pre_plug(VIRTIO_MD_PCI(dev), MACHINE(hotplug_dev), 
errp);
      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
+        uint8_t aw_bits = object_property_get_uint(OBJECT(dev),
+                                                   "aw-bits", &error_abort);
          hwaddr db_start = 0, db_end = 0;
          QList *reserved_regions;
          char *resv_prop_str;

+ if (!aw_bits) {

+            qdev_prop_set_uint8(dev, "aw-bits", 48);
+        }
+
          if (vms->iommu != VIRT_IOMMU_NONE) {
              error_setg(errp, "virt machine does not support multiple IOMMUs");
              return;
diff --git a/hw/core/machine.c b/hw/core/machine.c
index fb5afdcae4..70ac96954c 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -30,9 +30,12 @@
  #include "exec/confidential-guest-support.h"
  #include "hw/virtio/virtio-pci.h"
  #include "hw/virtio/virtio-net.h"
+#include "hw/virtio/virtio-iommu.h"
  #include "audio/audio.h"

-GlobalProperty hw_compat_8_2[] = {};

+GlobalProperty hw_compat_8_2[] = {
+    { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "64" },
+};
  const size_t hw_compat_8_2_len = G_N_ELEMENTS(hw_compat_8_2);

GlobalProperty hw_compat_8_1[] = {

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 196827531a..ee2d379c90 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1456,6 +1456,8 @@ static void pc_machine_device_pre_plug_cb(HotplugHandler 
*hotplug_dev,
      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MD_PCI)) {
          virtio_md_pci_pre_plug(VIRTIO_MD_PCI(dev), MACHINE(hotplug_dev), 
errp);
      } else if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
+        uint8_t aw_bits = object_property_get_uint(OBJECT(dev),
+                                                   "aw-bits", &error_abort);
          /* Declare the APIC range as the reserved MSI region */
          char *resv_prop_str = g_strdup_printf("0xfee00000:0xfeefffff:%d",
                                                VIRTIO_IOMMU_RESV_MEM_T_MSI);
@@ -1464,6 +1466,10 @@ static void pc_machine_device_pre_plug_cb(HotplugHandler 
*hotplug_dev,
          qlist_append_str(reserved_regions, resv_prop_str);
          qdev_prop_set_array(dev, "reserved-regions", reserved_regions);

+ if (!aw_bits) {

+            qdev_prop_set_uint8(dev, "aw-bits", VTD_HOST_AW_39BIT);
+        }
+
          g_free(resv_prop_str);
      }

diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c

index 7870bdbeee..c468e9b13b 100644
--- a/hw/virtio/virtio-iommu.c
+++ b/hw/virtio/virtio-iommu.c
@@ -1529,7 +1529,7 @@ static Property virtio_iommu_properties[] = {
      DEFINE_PROP_LINK("primary-bus", VirtIOIOMMU, primary_bus,
                       TYPE_PCI_BUS, PCIBus *),
      DEFINE_PROP_BOOL("boot-bypass", VirtIOIOMMU, boot_bypass, true),
-    DEFINE_PROP_UINT8("aw-bits", VirtIOIOMMU, aw_bits, 64),
+    DEFINE_PROP_UINT8("aw-bits", VirtIOIOMMU, aw_bits, 0),
      DEFINE_PROP_END_OF_LIST(),
  };