[RFC PATCH 4/7] iommu/riscv: Program QoS IDs for assigned groups

[Zhanpeng Zhang]

Hi Drew,

On 8/9/26 1:07 AM, Drew Fustini wrote:
> On Tue, Jul 14, 2026 at 09:06:54PM +0800, Zhanpeng Zhang wrote:
>> Program RCID and MCID for RISC-V IOMMU groups through the device context
>> TA fields. The resctrl group assignment is per device group, so reject
>> BARE mode where only the per-IOMMU iommu_qosid global default is
>> available.
>>
>> Validate every group member, firmware ID, device context, field value,
>> and QoS ID capability before changing hardware. Then update all members
>> through the checked IOMMU group helper so a validation failure leaves the
>> group unchanged.
>>
>> Serialize DC.ta changes with context setup under qosid_lock. Change only
>> the RCID and MCID fields with ordinary accesses so fixed DDT mappings are
>> not subject to atomic LR/SC operations, invalidate active device contexts
>> after an update, and clear the IDs when a device is released.
>>
>> Signed-off-by: Zhanpeng Zhang <zhangzhanpeng.jasper at bytedance.com>
>> ---
>>   arch/riscv/include/asm/qos.h     |  16 +++
>>   drivers/iommu/riscv/iommu-bits.h |  15 +++
>>   drivers/iommu/riscv/iommu.c      | 200 ++++++++++++++++++++++++++++++-
>>   drivers/iommu/riscv/iommu.h      |   3 +
>>   4 files changed, 232 insertions(+), 2 deletions(-)
>>
> [..]
>> +static void riscv_iommu_dc_update_qosid(struct riscv_iommu_device *iommu,
>> +					struct riscv_iommu_dc *dc,
>> +					u32 rcid, u32 mcid)
>> +{
>> +	u64 qos_ta = riscv_iommu_qosid_ta(rcid, mcid);
>> +	u64 ta;
>> +
>> +	lockdep_assert_held(&iommu->qosid_lock);
>
> It seems that qosid_lock is not defined until the next patch. I think
> you should move the definition to this patch so that the series is
> bisectable.
>
> Thanks,
> Drew

You're right. qosid_lock is first used in this patch, so its definition
should be added here as well. I will fix the patch ordering in v2.

Thanks,
Zhanpeng