Re: [PATCH 01/11] hw/arm/smmuv3-accel: Add helper for resolving auto parameters

[Nathan Chen <nathanc@nvidia.com>]

On 4/10/2026 12:37 AM, Eric Auger wrote:
> 
> On 4/1/26 3:02 AM, Nathan Chen wrote:
>> From: Nathan Chen<nathanc@nvidia.com>
>>
>> Introduce smmuv3_accel_auto_finalise() to resolve properties that are
>> set to 'auto' for accelerated SMMUv3. This helper function allows
>> properties such as ats, ril, ssidsize, and oas support to be resolved
>> from host IOMMU capabilities via IOMMU_GET_HW_INFO.
>>
>> Auto mode requires at least one cold-plugged device to retrieve and
>> finalise these properties. Register a machine_init_done notifier to
>> verify this requirement and fail boot if it is not met.
>>
>> Hot-plugged devices into an accel SMMUv3-associated bus will re-use
>> the resolved host values from the initial cold-plug.
>>
>> Subsequent patches will make use of this helper to resolve 'auto' to
>> what is reported by host IOMMU capabilities.
>>
>> Suggested-by: Shameer Kolothum<skolothumtho@nvidia.com>
>> Signed-off-by: Nathan Chen<nathanc@nvidia.com>
>> ---
>>   hw/arm/smmuv3-accel.c   | 14 ++++++++++++++
>>   hw/arm/smmuv3-accel.h   |  2 ++
>>   hw/arm/smmuv3.c         | 20 ++++++++++++++++++++
>>   include/hw/arm/smmuv3.h |  2 ++
>>   4 files changed, 38 insertions(+)
>>
>> diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
>> index 65c2f44880..a0146c8d31 100644
>> --- a/hw/arm/smmuv3-accel.c
>> +++ b/hw/arm/smmuv3-accel.c
>> @@ -35,11 +35,25 @@ static int smmuv3_oas_bits(uint32_t oas)
>>       return map[oas];
>>   }
>>   
>> +static void smmuv3_accel_auto_finalise(SMMUv3State *s,
>> +                                       struct iommu_hw_info_arm_smmuv3 *info) {
>> +    SMMUv3AccelState *accel = s->s_accel;
>> +
>> +    /* Return if no auto for any or finalised already */
>> +    if (!accel->auto_mode || accel->auto_finalised) {
>> +        return;
>> +    }
>> +
>> +    accel->auto_finalised = true;
>> +}
>> +
>>   static bool
>>   smmuv3_accel_check_hw_compatible(SMMUv3State *s,
>>                                    struct iommu_hw_info_arm_smmuv3 *info,
>>                                    Error **errp)
>>   {
>> +    smmuv3_accel_auto_finalise(s, info);
>> +
>>       /* QEMU SMMUv3 supports both linear and 2-level stream tables */
>>       if (FIELD_EX32(info->idr[0], IDR0, STLEVEL) !=
>>                   FIELD_EX32(s->idr[0], IDR0, STLEVEL)) {
>> diff --git a/hw/arm/smmuv3-accel.h b/hw/arm/smmuv3-accel.h
>> index dba6c71de5..3c1cd55714 100644
>> --- a/hw/arm/smmuv3-accel.h
>> +++ b/hw/arm/smmuv3-accel.h
>> @@ -26,6 +26,8 @@ typedef struct SMMUv3AccelState {
>>       uint32_t bypass_hwpt_id;
>>       uint32_t abort_hwpt_id;
>>       QLIST_HEAD(, SMMUv3AccelDevice) device_list;
>> +    bool auto_mode;
>> +    bool auto_finalised;
>>   } SMMUv3AccelState;
>>   
>>   typedef struct SMMUS1Hwpt {
>> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
>> index 7fead1c3cf..09ea08eb18 100644
>> --- a/hw/arm/smmuv3.c
>> +++ b/hw/arm/smmuv3.c
>> @@ -37,6 +37,7 @@
>>   #include "smmuv3-accel.h"
>>   #include "smmuv3-internal.h"
>>   #include "smmu-internal.h"
>> +#include "system/system.h"
>>   
>>   #define PTW_RECORD_FAULT(ptw_info, cfg) (((ptw_info).stage == SMMU_STAGE_1 && \
>>                                           (cfg)->record_faults) || \
>> @@ -2020,6 +2021,22 @@ static bool smmu_validate_property(SMMUv3State *s, Error **errp)
>>       return true;
>>   }
>>   
>> +static void smmuv3_machine_done(Notifier *notifier, void *data)
>> +{
>> +    SMMUv3State *s = container_of(notifier, SMMUv3State, machine_done);
>> +    SMMUv3AccelState *accel = s->s_accel;
>> +
>> +    if (!s->accel) {
>> +        return;
>> +    }
>> +
>> +    if (accel->auto_mode && !accel->auto_finalised) {
>> +        error_report("arm-smmuv3 accel=on with 'auto' properties requires "
>> +                     "at least one cold-plugged VFIO device");
>> +        exit(1);
>> +    }
>> +}
>> +
>>   static void smmu_realize(DeviceState *d, Error **errp)
>>   {
>>       SMMUState *sys = ARM_SMMU(d);
>> @@ -2058,6 +2075,9 @@ static void smmu_realize(DeviceState *d, Error **errp)
>>   
>>       smmu_init_irq(s, dev);
>>       smmuv3_init_id_regs(s);
>> +
>> +    s->machine_done.notify = smmuv3_machine_done;
>> +    qemu_add_machine_init_done_notifier(&s->machine_done);
> you might also register the machine done notifier only in case auto_mode
> is set
Yes, I'll incorporate this in the next revision.

Thanks,
Nathan