Re: [PATCH v7 0/2] RISC-V IOMMU HPM support

[Zong Li]

On Fri, Aug 28, 2026 at 4:49 PM Guo Ren <guoren@xxxxxxxxxx> wrote:
>
> Hi Li Zong,
>
> Just two patches? Where did the riscv-iommu PMU driver patch go?
>

I apologize for missing the first commit. I will resend it as PATCH
RESEND v7. Thank you very much for pointing this out!

> --
> Best Regards
>  GUO Ren
>
> On Fri, Aug 28, 2026 at 3:07 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. Therefore, the child driver
> > can obtain resources and information from the parent device, such as
> > the MMIO base address and IRQ number.
> >
> > The thrid commit adds raw spinlock for race condition when PCI MSI/MSI-X
> > on IMSIC. As the commit message mentioned:
> > Events are bound to one CPU and the interrupt is affine to it, so the
> > perf callbacks running with interrupts disabled would be enough to
> > exclude the handler. But PCI MSI/MSI-X on IMSIC breaks that:
> > The irqchip sets IRQCHIP_MOVE_DEFERRED, so irq_set_affinity() reports
> > success while only recording the request, and the move is applied in
> > interrupt context upon the next device interrupt. Until then the
> > interrupt is still routed to the CPU IMSIC picked initially, so the
> > first overflow interrupt can run concurrently with the perf callbacks
> > on the CPU the events are bound to.
> >
> > I noticed that xgene_pmu and arm-cci have similar implementation, so add
> > it in riscv_iommu_pmu should be accepted.
> >
> > Changed in v6:
> > - Rebased onto the latest v7.3-rc
> > - Use sysfs_emit instead of cpumap_print_to_pagebuf
> > - Set up on_cpu and irq affinity by cpuhp callbacks
> > - Change type of on_cpu from unsigned int to int
> > - Reject filter operands of cycle event in event_init
> > - Check return value of counter number and  masks in probe
> > - Add raw spinlock for race condition (third commit)
> >
> > Changed in v5:
> > - Pick up suggestions from sashiko-bot as follows
> > - Fix event group validation for sw event
> > - Bind IRQ to aux PMU dev instead of parent IOMMU dev
> > - Clear OF bit when event is NULL
> > - Improve hi-lo-hi patten
> > - Add back IRQF_SHARED flag due to mismatch
> > - Manage cpuhp and pmu register by devre
> >
> > Changed in v4:
> > - Rebased onto v7.3-rc
> > - Use is_sampling_event() instead of accessing vairable directly
> > - Rename the matching name from "iommu.pmu" to "riscv-iommu.pmu"
> > - Change the naming of PMU device for avoid ":" in PCIe case
> > - Add suppress_bind_attrs attribute
> > - Remove IRQF_SHARED flag
> > - Set irq affinity to local CPU of IOMMU
> > - Allocate ID by IDA for auxiliary device
> > - Pick up suggestions from sashiko-bot
> >
> > Changed in v3:
> > - Rebased onto v7.2-rc3
> > - Use hi_lo_writeq/readq to access register
> > - Pick comments from sashiko-bot as follows
> > - Set IRQ CPU affinity
> > - Remove IRQF_ONESHOT flag when request irq
> > - Adjust cycle event check by checking event_id field only
> > - Fix bug for group events verificaiton
> > - Fix KASAN issue about casting 32-bit variable to unsigned long pointer
> > - Clear IPSR pending bit before starting counter
> > - Clear OF bit in event selector register in irq handler
> > - Release irq by devm instead of explicit free_irq
> >
> > Changed in v2:
> > - Rebased onto v7.2-rc1
> > - Use hi-lo-hi mechanism to read counter.
> >   Suggested by Guo Ren and David Laight
> >
> > 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):
> >   iommu/riscv: create a auxiliary device for HPM
> >   drivers/perf: riscv-iommu: protect shared state with a raw spinlock
> >
> >  drivers/iommu/riscv/Kconfig    |  1 +
> >  drivers/iommu/riscv/iommu.c    | 37 +++++++++++++++++++
> >  drivers/perf/riscv_iommu_pmu.c | 66 ++++++++++++++++++++++++++++++----
> >  3 files changed, 98 insertions(+), 6 deletions(-)
> >
> > --
> > 2.43.7
> >