Re: [PATCH v2 0/2] RISC-V IOMMU HPM support

[Zong Li]

On Sun, Feb 8, 2026 at 2:38 PM Zong Li <zong.li@xxxxxxxxxx> wrote:
>
> This series implements support for the RISC-V IOMMU hardware performance
> monitor.
>
> The RISC-V IOMMU PMU driver is implemented as an auxiliary device driver
> created by the parent RISC-V IOMMU driver. The child driver can obtain
> resources and information from the parent device, such as the MMIO base
> address and IRQ number.
>
> Custom event support is not included in this series and will be submitted
> as a separate series. The idea is that custom events will be defined
> through the driver data of the auxiliary driver. When the parent IOMMU
> driver creates the auxiliary device, it should pass a vendor-specific
> name as the device name in order to match the corresponding auxiliary
> device ID.
>
> After my initial RFC and the v1 patch series were posted, similar patch
> series also appeared on the mailing list.
>
> One was from Yaxing Guo:
> https://lore.kernel.org/all/20250915020911.1313-1-guoyaxing@xxxxxxxxxx/
>
> and another from Lv Zheng:
> https://lore.kernel.org/all/30C7AD351DB55276+a8b03dac-c5af-4034-8631-ac1c352a469f@xxxxxxxxxxxxxxxxxx/
>
> Yaxing has agreed to pause his series, as discussed here:
> https://lore.kernel.org/linux-iommu/2ce9d8be-10b3-48dd-b99e-7358347fc171@xxxxxxxxxx/
>
> The motivation for sending this v2 version is not only to address the
> feedback and suggestions from the previous round, but also to introduce
> a major structural change: the PMU driver has been moved under
> drivers/perf/, which has been mentioned repeatedly by several people.
> This results in a different driver structure compared to my earlier
> version and the other two series, and I'd like to gather feedback and
> suggestions from the community on this approach. If the community would
> prefer to go with Lv Zheng’s version instead, I am perfectly fine with
> that as well.
>
> Since I did not follow up closely on the patches from Lv Zheng, Jingyu
> Li, or Yaxing, it is possible that this v2 series may miss some important
> features or fixes from their work. Therefore, I would really appreciate
> it if everyone could help review this v2 series and point out any
> additional fixes or feature support that I may have missed.
>

Hi Robin,

This is the next version of the previous series. It seems to me that
this v2 version addresses all the suggestions you mentioned in the
previous series.
https://lore.kernel.org/lkml/20250115030306.29735-1-zong.li@xxxxxxxxxx/

I talked with Lv Zheng, we'd like to know if this version looks good
to you, or if there is anything else that could be improved?

Thanks.

> Changed in v1:
> - Rebased onto v6.19-rc8
> - Pick all suggestions and feedbacks from v1 series
> - Add cpu hotplug implementation to avoid race enablement
> - Move PMU-related definition from header to c file
> - Change PMU driver to auxiliary device driver
>
> Changed in RFC:
> - Rebase onto v6.13-rc7
> - Clear interrupt pending before handling interrupt
> - Fix the counter value issue caused by OF bit in the cycle counter.
> - Invoke riscv_iommu_hpm_disable() instead of riscv_iommu_pmu_uninit()
>   in riscv_iommu_remove()
>
> Zong Li (2):
>   drivers/perf: riscv-iommu: add risc-v iommu pmu driver
>   iommu/riscv: create a auxiliary device for HPM
>
>  drivers/iommu/riscv/iommu-bits.h |  61 ---
>  drivers/iommu/riscv/iommu.c      |  20 +
>  drivers/perf/Kconfig             |  12 +
>  drivers/perf/Makefile            |   1 +
>  drivers/perf/riscv_iommu_pmu.c   | 661 +++++++++++++++++++++++++++++++
>  5 files changed, 694 insertions(+), 61 deletions(-)
>  create mode 100644 drivers/perf/riscv_iommu_pmu.c
>
> --
> 2.43.7
>