linux-kernel - Re: [PATCH V3 0/7] iommu/vt-d: Support performance monitoring for IOMMU

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Date:   Sat, 28 Jan 2023 15:10:09 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     kan.liang@...ux.intel.com, joro@...tes.org, will@...nel.org,
        dwmw2@...radead.org, robin.murphy@....com, robert.moore@...el.com,
        rafael.j.wysocki@...el.com, lenb@...nel.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Cc:     baolu.lu@...ux.intel.com, yu-cheng.yu@...el.com
Subject: Re: [PATCH V3 0/7] iommu/vt-d: Support performance monitoring for
 IOMMU

On 2023/1/21 0:54, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> Changes since V2:
> - Move ecmd_submit_sync() to iommu.c to avoid #ifdef CONFIG_INTEL_IOMMU
> 
> Changes since V1:
> - The cap and ecap registers are always in the first page. It's not
>    necessary to use the reg size in dmar_validate_one_drhd(). (Patch 1)
> - Move reg_size up and pair it with reg_base_addr in struct
>    dmar_drhd_unit (Patch 1)
> - Update the year of Copyright (Patch 2)
> - Return 0 if PMS is not supported (Patch 2)
> - Refine the comments and add a pr_warn for per-counter capabilities
>    check (Patch 2)
> - Remove unnecessary iommu_pmu->num_cntr = i (Patch 2)
> - Remove has_ob of ecmd_submit_sync() (Patch 3)
> - Remove the helpers from non-INTEL_IOMMU. (Patch 3)
> - Still keep #ifdef CONFIG_INTEL_IOMMU for ecmd_submit_sync() to
>    avoid compile warning with non-INTEL_IOMMU config.
> - Use pr_warn_once() to replace WARN_ONCE() (Patch 4 & 6)
> - Free iommu PMU if it fails to be registered. (Patch 4)
> - Remove unnecessary 'handled' variable. (Patch 6)
> 
> A performance monitoring infrastructure, perfmon, is introduced with
> the VT-d Spec 4.0. The purpose of perfmon is to support collection of
> information about key events occurring during operation of the remapping
> hardware, to aid performance tuning and debug. The patch series is to
> support the perfmon for IOMMU.
> 
> To facilitate the perfmon support, the patch series also supports two
> new generic features of VT-d Spec 4.0.
> - Support the 'size' field to retrieve the accurate size of the register
>    set for each dmar device from DRHD. (Patch 1)
> - Support the new Enhanced Command Interface. (Patch 3)
> 
> With the patch series, users can collect the performance data of IOMMU
> via Linux perf tool. For example,
> 
>   $ perf stat -e dmar0/iommu_requests,filter_ats=0/ -a sleep 1
> 
>   Performance counter stats for 'system wide':
> 
>                2135      dmar0/iommu_requests,filter_ats=0/
> 
>         1.001087695 seconds time elapsed
> 
> The IOMMU PMUs can be found under /sys/bus/event_source/devices/dmar*
> 
> The available filters and event format can be found at the format folder
>   $ ls /sys/bus/event_source/devices/dmar0/format/
> event  event_group  filter_ats  filter_page_table
> 
> The supported events can be found at the events folder
> 
>   $ ls /sys/bus/event_source/devices/dmar0/events/
> ats_blocked        int_cache_hit_nonposted  iommu_mrds
> pasid_cache_lookup
> ctxt_cache_hit     int_cache_hit_posted     iommu_requests
> pg_req_posted
> ctxt_cache_lookup  int_cache_lookup         iotlb_hit
> pw_occupancy
> fs_nonleaf_hit     iommu_clocks             iotlb_lookup
> ss_nonleaf_hit
> fs_nonleaf_lookup  iommu_mem_blocked        pasid_cache_hit
> ss_nonleaf_lookup
> 
> Kan Liang (7):
>    iommu/vt-d: Support size of the register set in DRHD
>    iommu/vt-d: Retrieve IOMMU perfmon capability information
>    iommu/vt-d: Support Enhanced Command Interface
>    iommu/vt-d: Add IOMMU perfmon support
>    iommu/vt-d: Support cpumask for IOMMU perfmon
>    iommu/vt-d: Add IOMMU perfmon overflow handler support
>    iommu/vt-d: Enable IOMMU perfmon support
> 
>   .../sysfs-bus-event_source-devices-iommu      |  32 +
>   drivers/iommu/intel/Kconfig                   |   9 +
>   drivers/iommu/intel/Makefile                  |   1 +
>   drivers/iommu/intel/dmar.c                    |  33 +-
>   drivers/iommu/intel/iommu.c                   |  59 ++
>   drivers/iommu/intel/iommu.h                   | 101 +-
>   drivers/iommu/intel/perfmon.c                 | 860 ++++++++++++++++++
>   drivers/iommu/intel/perfmon.h                 |  65 ++
>   drivers/iommu/intel/svm.c                     |   2 +-
>   include/acpi/actbl1.h                         |   2 +-
>   include/linux/cpuhotplug.h                    |   1 +
>   include/linux/dmar.h                          |   1 +
>   12 files changed, 1159 insertions(+), 7 deletions(-)
>   create mode 100644 Documentation/ABI/testing/sysfs-bus-event_source-devices-iommu
>   create mode 100644 drivers/iommu/intel/perfmon.c
>   create mode 100644 drivers/iommu/intel/perfmon.h

Thanks for the work. The overall looks good to me now. But I am still
seeing some code style issues after running "./scripts/checkpatch.pl
--strict" scripts.

Can you please fix those issues and post a v4?

Best regards,
baolu