Re: [PATCH v2 3/3] hw: Set virtio-iommu aw-bits default value on pc_q35_9.0 and arm virt

[Eric Auger]

Hi Zhenzhong,

On 2/2/24 07:51, Duan, Zhenzhong wrote:
> Hi Eric,
>
>> -----Original Message-----
>> From: Eric Auger <eric.auger@redhat.com>
>> pc_q35_9.0 and arm virt
>>
>> 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.auger@redhat.com>
>>
>> ---
>>
>> 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 e6ead2c5c8..56539f2fc5 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -2718,10 +2718,16 @@ 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", NULL);
>>         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 803244e5cc..0e2bcb4840 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1458,6 +1458,8 @@ 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", NULL);
>>         /* 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);
>> @@ -1466,6 +1468,10 @@ 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", 39);
>> +        }
>> +
>>         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),
> Not clear if virtio-iommu support other archs besides x86 and arm.
> It looks on those archs, aw_bits is default 0 on machine 9.0 above
> and will fails the check in realize?

At the moment the virtio-iommu only is supported along with q35 and
arm-virt.
Only those machines set the reserved-regions prop and the aw-bits, which
are both requested for a correct behavior.

Thank you for the review!

Eric

>
> Thanks
> Zhenzhong
>
>>     DEFINE_PROP_END_OF_LIST(),
>> };
>>
>> --
>> 2.41.0