Messages in this thread | | | Subject | Re: [PATCH 2/2] iommu/amd: Remove performance counter pre-initialization test | From | Shuah Khan <> | Date | Fri, 9 Apr 2021 14:19:57 -0600 |
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On 4/9/21 2:00 PM, Shuah Khan wrote: > On 4/9/21 2:58 AM, Suravee Suthikulpanit wrote: >> In early AMD desktop/mobile platforms (during 2013), when the IOMMU >> Performance Counter (PMC) support was first introduced in >> commit 30861ddc9cca ("perf/x86/amd: Add IOMMU Performance Counter >> resource management"), there was a HW bug where the counters could not >> be accessed. The result was reading of the counter always return zero. >> >> At the time, the suggested workaround was to add a test logic prior >> to initializing the PMC feature to check if the counters can be >> programmed >> and read back the same value. This has been working fine until the more >> recent desktop/mobile platforms start enabling power gating for the PMC, >> which prevents access to the counters. This results in the PMC support >> being disabled unnecesarily. >> >> Unfortunatly, there is no documentation of since which generation >> of hardware the original PMC HW bug was fixed. Although, it was fixed >> soon after the first introduction of the PMC. Base on this, we assume >> that the buggy platforms are less likely to be in used, and it should >> be relatively safe to remove this legacy logic. >> >> Link: >> https://lore.kernel.org/linux-iommu/alpine.LNX.3.20.13.2006030935570.3181@monopod.intra.ispras.ru/ >> >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753 >> Cc: Tj (Elloe Linux) <ml.linux@elloe.vision> >> Cc: Shuah Khan <skhan@linuxfoundation.org> >> Cc: Alexander Monakov <amonakov@ispras.ru> >> Cc: David Coe <david.coe@live.co.uk> >> Cc: Paul Menzel <pmenzel@molgen.mpg.de> >> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com> >> --- > > > Tested-by: Shuah Khan <skhan@linuxfoundation.org> >
Revert + this patch - same as my test on Ryzen 5
On AMD Ryzen 7 4700G with Radeon Graphics
These look real odd to me. Let me know if I should look further.
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':
17,761,952,514,865,374 amd_iommu_0/cmd_processed/ (33.28%) 18,582,155,570,607,472 amd_iommu_0/cmd_processed_inv/ (33.32%) 0 amd_iommu_0/ign_rd_wr_mmio_1ff8h/ (33.36%) 5,056,087,645,262,255 amd_iommu_0/int_dte_hit/ (33.40%) 32,831,106,446,308,888 amd_iommu_0/int_dte_mis/ (33.44%) 13,461,819,655,591,296 amd_iommu_0/mem_dte_hit/ (33.45%) 208,555,436,221,050,464 amd_iommu_0/mem_dte_mis/ (33.47%) 196,824,154,635,609,888 amd_iommu_0/mem_iommu_tlb_pde_hit/ (33.46%) 193,552,630,440,410,144 amd_iommu_0/mem_iommu_tlb_pde_mis/ (33.45%) 176,936,647,809,098,368 amd_iommu_0/mem_iommu_tlb_pte_hit/ (33.41%) 184,737,401,623,626,464 amd_iommu_0/mem_iommu_tlb_pte_mis/ (33.37%) 0 amd_iommu_0/mem_pass_excl/ (33.33%) 0 amd_iommu_0/mem_pass_pretrans/ (33.30%) 0 amd_iommu_0/mem_pass_untrans/ (33.28%) 0 amd_iommu_0/mem_target_abort/ (33.27%) 245,383,212,924,004,288 amd_iommu_0/mem_trans_total/ (33.27%) 0 amd_iommu_0/page_tbl_read_gst/ (33.28%) 262,267,045,917,967,264 amd_iommu_0/page_tbl_read_nst/ (33.27%) 256,308,216,913,137,600 amd_iommu_0/page_tbl_read_tot/ (33.28%) 0 amd_iommu_0/smi_blk/ (33.27%) 0 amd_iommu_0/smi_recv/ (33.27%) 0 amd_iommu_0/tlb_inv/ (33.27%) 0 amd_iommu_0/vapic_int_guest/ (33.26%) 38,913,544,420,579,888 amd_iommu_0/vapic_int_non_guest/ (33.27%)
10.003967760 seconds time elapsed
thanks, -- Shuah
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