Re: [PATCH 2/2] iommu/amd: Remove performance counter pre-initialization test

[David Coe]

Results for AMD Ryzen 4700U running Ubuntu 21.04β kernel 5.11.0-13

$ sudo dmesg | grep IOMMU
[    0.490352] pci 0000:00:00.2: AMD-Vi: IOMMU performance counters 
supported
[    0.491985] pci 0000:00:00.2: AMD-Vi: Found IOMMU cap 0x40
[    0.493732] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 
counters/bank).
[    0.793259] AMD-Vi: AMD IOMMUv2 driver by Joerg Roedel <jroedel@xxxxxxx>

$ systool -m kvm_amd -v
Module = "kvm_amd"

  Attributes:
    coresize            = "114688"
    initsize            = "0"
    initstate           = "live"
    refcnt              = "0"
    srcversion          = "4371BA17A41823101F90761"
    taint               = ""
    uevent              = <store method only>

  Parameters:
    avic                = "0"
    dump_invalid_vmcb   = "N"
    nested              = "1"
    npt                 = "1"
    nrips               = "1"
    pause_filter_count_grow= "2"
    pause_filter_count_max= "65535"
    pause_filter_count_shrink= "0"
    pause_filter_count  = "3000"
    pause_filter_thresh = "128"
    sev_es              = "0"
    sev                 = "0"
    vgif                = "1"
    vls                 = "1"

  Sections:

$ compgen -G "/sys/kernel/iommu_groups/*/devices/*"
/sys/kernel/iommu_groups/0/devices/0000:00:01.0
/sys/kernel/iommu_groups/2/devices/0000:00:02.2
/sys/kernel/iommu_groups/4/devices/0000:00:08.2
/sys/kernel/iommu_groups/4/devices/0000:03:00.2
/sys/kernel/iommu_groups/4/devices/0000:04:00.0
/sys/kernel/iommu_groups/4/devices/0000:03:00.4
/sys/kernel/iommu_groups/4/devices/0000:03:00.6
/sys/kernel/iommu_groups/4/devices/0000:00:08.1
/sys/kernel/iommu_groups/4/devices/0000:03:00.1
/sys/kernel/iommu_groups/4/devices/0000:03:00.3
/sys/kernel/iommu_groups/4/devices/0000:04:00.1
/sys/kernel/iommu_groups/4/devices/0000:03:00.5
/sys/kernel/iommu_groups/4/devices/0000:00:08.0
/sys/kernel/iommu_groups/4/devices/0000:03:00.0
/sys/kernel/iommu_groups/6/devices/0000:00:18.5
/sys/kernel/iommu_groups/6/devices/0000:00:18.7
/sys/kernel/iommu_groups/6/devices/0000:00:18.0
/sys/kernel/iommu_groups/6/devices/0000:00:18.2
/sys/kernel/iommu_groups/6/devices/0000:00:18.4
/sys/kernel/iommu_groups/6/devices/0000:00:18.6
/sys/kernel/iommu_groups/6/devices/0000:00:18.1
/sys/kernel/iommu_groups/6/devices/0000:00:18.3
/sys/kernel/iommu_groups/8/devices/0000:02:00.0
/sys/kernel/iommu_groups/1/devices/0000:00:02.0
/sys/kernel/iommu_groups/3/devices/0000:00:02.4
/sys/kernel/iommu_groups/5/devices/0000:00:14.0
/sys/kernel/iommu_groups/5/devices/0000:00:14.3
/sys/kernel/iommu_groups/7/devices/0000:01:00.0

$ sudo perf stat -e 'amd_iommu_0/cmd_processed/, 
amd_iommu_0/cmd_processed_inv/, amd_iommu_0/ign_rd_wr_mmio_1ff8h/, 
amd_iommu_0/int_dte_hit/, amd_iommu_0/int_dte_mis/, 
amd_iommu_0/mem_dte_hit/, amd_iommu_0/mem_dte_mis/, 
amd_iommu_0/mem_iommu_tlb_pde_hit/, amd_iommu_0/mem_iommu_tlb_pde_mis/, 
amd_iommu_0/mem_iommu_tlb_pte_hit/, amd_iommu_0/mem_iommu_tlb_pte_mis/, 
amd_iommu_0/mem_pass_excl/, amd_iommu_0/mem_pass_pretrans/, 
amd_iommu_0/mem_pass_untrans/, amd_iommu_0/mem_target_abort/, 
amd_iommu_0/mem_trans_total/, amd_iommu_0/page_tbl_read_gst/, 
amd_iommu_0/page_tbl_read_nst/, amd_iommu_0/page_tbl_read_tot/, 
amd_iommu_0/smi_blk/, amd_iommu_0/smi_recv/, amd_iommu_0/tlb_inv/, 
amd_iommu_0/vapic_int_guest/, amd_iommu_0/vapic_int_non_guest/' sleep 10

Performance counter stats for 'system wide':

                12      amd_iommu_0/cmd_processed/             (33.28%)
                 6       amd_iommu_0/cmd_processed_inv/        (33.32%)
                 0       amd_iommu_0/ign_rd_wr_mmio_1ff8h/     (33.36%)
               290       amd_iommu_0/int_dte_hit/              (33.40%)
                20       amd_iommu_0/int_dte_mis/              (33.46%)
               391       amd_iommu_0/mem_dte_hit/              (33.49%)
             3,720       amd_iommu_0/mem_dte_mis/              (33.49%)
                44       amd_iommu_0/mem_iommu_tlb_pde_hit/    (33.46%)
               810       amd_iommu_0/mem_iommu_tlb_pde_mis/    (33.45%)
                35       amd_iommu_0/mem_iommu_tlb_pte_hit/    (33.41%)
               746       amd_iommu_0/mem_iommu_tlb_pte_mis/    (33.37%)
                 0       amd_iommu_0/mem_pass_excl/            (33.32%)
                 0       amd_iommu_0/mem_pass_pretrans/        (33.28%)
                 0       amd_iommu_0/mem_pass_untrans/         (33.28%)
                 0       amd_iommu_0/mem_target_abort/         (33.27%)
               715       amd_iommu_0/mem_trans_total/          (33.27%)
                 0       amd_iommu_0/page_tbl_read_gst/        (33.28%)
                36       amd_iommu_0/page_tbl_read_nst/        (33.27%)
                36       amd_iommu_0/page_tbl_read_tot/        (33.27%)
                 0       amd_iommu_0/smi_blk/                  (33.28%)
                 0       amd_iommu_0/smi_recv/                 (33.26%)
                 0       amd_iommu_0/tlb_inv/                  (33.23%)
                 0       amd_iommu_0/vapic_int_guest/          (33.24%)
               366       amd_iommu_0/vapic_int_non_guest/      (33.27%)

The immediately obvious difference is the with the enormous count seen 
on mem_dte_mis on the older Ryzen 2400G. Will do some RTFM but anyone 
with comments and insight?

841,689,151,202,939       amd_iommu_0/mem_dte_mis/              (33.44%)

Otherwise, all seems to running smoothly (especially for a distribution 
still in β). Bravo and many thanks all!

--
David Coe