Re: iommu/amd: bug report: page table memory leak

[Daniel Jordan <daniel.m.jordan@oracle.com>]

Friendly ping.  Any thoughts about this report?

thanks,
Daniel

On Tue, Jan 18, 2022 at 02:47:20PM -0500, Daniel Jordan wrote:
> Hi,
> 
> I've hit a memory leak while testing qemu v6.2.0-rc4 on an AMD EPYC 7J13
> (Milan) system.  Starting an almost 1T guest, the leak is over 1.5G per
> qemu invocation.  I haven't checked whether the leak is proportional to
> guest size.  It happens with a vfio device, and only when the guest's
> memory is preallocated using qemu prealloc (this latter part is kinda
> strange).  It happens when the guest memory uses THP but not hugetlb.
> 
> Bisection:
> 
> # bad: [df0cc57e057f18e44dac8e6c18aba47ab53202f9] Linux 5.16                
> # good: [f40ddce88593482919761f74910f42f4b84c004b] Linux 5.11
> git bisect start 'df0cc57e057f1' 'f40ddce885934' '--' 'drivers/vfio' 'drivers/iommu' 'include/linux/amd-iommu.h' 'include/linux/dma-iommu.h' 'include/linux/intel-iommu.h' 'include/linux/iommu-helper.h' 'include/linux/of_iommu.h' 'include/
> linux/omap-iommu.h' 'include/linux/platform_data/iommu-omap.h' 'include/linux/iommu.h' 'include/trace/events/intel_iommu.h' 'include/trace/events/iommu.h' 'include/uapi/linux/iommu.h' 'include/uapi/linux/virtio_iommu.h' 'arch/x86/events/a
> md/iommu.h' 'arch/x86/events/amd/iommu.c' 'arch/x86/include/asm/iommu.h' 'arch/x86/include/asm/iommu_table.h' 'arch/x86/kernel/pci-iommu_table.c'
> # bad: [cee57d4fe74e82e784f6566bad3e3bb1ca51a211] iommu/vt-d: Remove unnecessary braces
> git bisect bad cee57d4fe74e82e784f6566bad3e3bb1ca51a211                           
> # bad: [9fb5fad562fa0a41c84691714d99c23f54168a9e] iommu: remove DOMAIN_ATTR_PAGING
> git bisect bad 9fb5fad562fa0a41c84691714d99c23f54168a9e                           
> # bad: [45e606f2726926b04094e1c9bf809bca4884c57f] Merge branches 'arm/renesas', 'arm/smmu', 'x86/amd', 'x86/vt-d' and 'core' into next
> git bisect bad 45e606f2726926b04094e1c9bf809bca4884c57f
> # good: [7060377ce06f9cd3ed6274c0f2310463feb5baec] Merge branch 'for-joerg/mtk' into for-joerg/arm-smmu/updates
> git bisect good 7060377ce06f9cd3ed6274c0f2310463feb5baec
> # bad: [6778ff5b21bd8e78c8bd547fd66437cf2657fd9b] iommu/amd: Fix performance counter initialization
> git bisect bad 6778ff5b21bd8e78c8bd547fd66437cf2657fd9b
> # good: [f9b4df790aa4372bfa11b7d212e537b763295429] iommu/amd: Declare functions as extern
> git bisect good f9b4df790aa4372bfa11b7d212e537b763295429
> # bad: [33aef9786046d9a5744cd1e8d5d0ce800d611fdc] iommu/amd: Rename variables to be consistent with struct io_pgtable_ops
> git bisect bad 33aef9786046d9a5744cd1e8d5d0ce800d611fdc       
> # bad: [e42ba0633064ef23eb1c8c21edf96bac1541bd4b] iommu/amd: Restructure code for freeing page table
> git bisect bad e42ba0633064ef23eb1c8c21edf96bac1541bd4b       
> # good: [18954252a1d0b12e1b77087b55c37fb43b09e12a] iommu/amd: Move IO page table related functions
> git bisect good 18954252a1d0b12e1b77087b55c37fb43b09e12a      
> # first bad commit: [e42ba0633064ef23eb1c8c21edf96bac1541bd4b] iommu/amd: Restructure code for freeing page table
> 
> commit e42ba0633064ef23eb1c8c21edf96bac1541bd4b                         
> Author: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>                            
> Date:   Tue Dec 15 01:36:59 2020 -0600                                  
>                                                                                          
>     iommu/amd: Restructure code for freeing page table                    
>                                                                                          
>     By consolidate logic into v1_free_pgtable helper function,            
>     which is called from IO page table framework.                                        
>                                                                             
>     Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
>     Link: https://lore.kernel.org/r/20201215073705.123786-8-suravee.suthikulpanit@amd.com
>     Signed-off-by: Joerg Roedel <jroedel@suse.de>                         
>                                                                             
>  drivers/iommu/amd/amd_iommu.h  |  1 -                                    
>  drivers/iommu/amd/io_pgtable.c | 41 ++++++++++++++++++++++++-----------------
>  drivers/iommu/amd/iommu.c      | 21 ++++-----------------                
>  3 files changed, 28 insertions(+), 35 deletions(-)                         
> 
> Qemu command line:
> 
> numactl -m 1 -N 1 "$QEMU" \
>     -name vmol74 \
>     -machine q35,accel=kvm,usb=off,dump-guest-core=off,memory-backend=pc.ram \
>     -cpu host,host-phys-bits=true \
>     -smp cpus=32 \
>     -no-user-config \
>     -nodefaults \
>     -rtc base=utc,driftfix=slew \
>     -global kvm-pit.lost_tick_policy=delay \
>     -no-hpet \
>     -no-shutdown \
>     -boot strict=on \
>     -drive file=${vm_image},format=raw,if=none,id=drive-ide0-0-0 \
>     -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=2 \
>     -device vfio-pci,host=${pci_addr},id=net2,bus=pcie.0 \
>     -msg timestamp=on \
>     -nographic \
>     -object memory-backend-ram,id=pc.ram,size=980g,prealloc=on,prealloc-threads=16 -m 980g \
>     -daemonize
> 
> Kernel config attached, and I can provide other details too if I left
> anything out.
> 
> thanks,
> Daniel


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