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Subject: Re: [PATCH 2/2] iommu/amd: Remove performance counter
 pre-initialization test
To:     Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
Cc:     joro@8bytes.org, will@kernel.org, jsnitsel@redhat.com,
        pmenzel@molgen.mpg.de, Jon.Grimm@amd.com,
        Tj <ml.linux@elloe.vision>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Alexander Monakov <amonakov@ispras.ru>,
        Alex Hung <1917203@bugs.launchpad.net>
References: <20210409085848.3908-1-suravee.suthikulpanit@amd.com>
 <20210409085848.3908-3-suravee.suthikulpanit@amd.com>
From:   David Coe <david.coe@live.co.uk>
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Date:   Tue, 13 Apr 2021 10:38:02 +0100
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Hi Suravee!

Just in case (!), I've run your revert+update patch on kernel 5.11.0-13, 
Ubuntu 21.04β running on an AMD FX-8350 (pre Zen and IOMMUv2). As with 
the AMD Ryzen 2400G and 4700U, I'm finding no obvious issues.


$ sudo dmesg | grep IOMMU
[    0.948890] pci 0000:00:00.2: AMD-Vi: Found IOMMU cap 0x40
[    4.393773] AMD-Vi: AMD IOMMUv2 driver by Joerg Roedel <jroedel@suse.de>
[    4.393776] AMD-Vi: AMD IOMMUv2 functionality not available on this 
system


$ 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                = "0"
     vls                 = "0"

   Sections:


$ compgen -G "/sys/kernel/iommu_groups/*/devices/*"
/sys/kernel/iommu_groups/9/devices/0000:00:14.2
/sys/kernel/iommu_groups/0/devices/0000:00:00.0
/sys/kernel/iommu_groups/10/devices/0000:00:14.3
/sys/kernel/iommu_groups/2/devices/0000:00:04.0
/sys/kernel/iommu_groups/12/devices/0000:00:14.5
/sys/kernel/iommu_groups/4/devices/0000:00:0d.0
/sys/kernel/iommu_groups/14/devices/0000:00:16.0
/sys/kernel/iommu_groups/14/devices/0000:00:16.2
/sys/kernel/iommu_groups/6/devices/0000:00:12.0
/sys/kernel/iommu_groups/6/devices/0000:00:12.2
/sys/kernel/iommu_groups/16/devices/0000:02:00.0
/sys/kernel/iommu_groups/8/devices/0000:00:14.0
/sys/kernel/iommu_groups/1/devices/0000:00:02.0
/sys/kernel/iommu_groups/11/devices/0000:00:14.4
/sys/kernel/iommu_groups/3/devices/0000:00:0b.0
/sys/kernel/iommu_groups/13/devices/0000:00:15.3
/sys/kernel/iommu_groups/13/devices/0000:00:15.0
/sys/kernel/iommu_groups/13/devices/0000:06:00.0
/sys/kernel/iommu_groups/13/devices/0000:00:15.2
/sys/kernel/iommu_groups/13/devices/0000:07:00.0
/sys/kernel/iommu_groups/13/devices/0000:08:00.0
/sys/kernel/iommu_groups/13/devices/0000:00:15.1
/sys/kernel/iommu_groups/13/devices/0000:09:00.0
/sys/kernel/iommu_groups/5/devices/0000:00:11.0
/sys/kernel/iommu_groups/15/devices/0000:01:00.1
/sys/kernel/iommu_groups/15/devices/0000:01:00.0
/sys/kernel/iommu_groups/7/devices/0000:00:13.0
/sys/kernel/iommu_groups/7/devices/0000:00:13.2
/sys/kernel/iommu_groups/17/devices/0000:04:00.0


$ sudo kvm-ok
INFO: /dev/kvm exists
KVM acceleration can be used


$ perf list | grep iommu
No amd_iommu events

Best regards and many thanks.

-- 
David Coe