[Bug 1866962] Re: [Regression]Powerpc kvm guest unable to start with hugepage backed memory

[Satheesh Rajendran]

** Summary changed:

- Powerpc kvm guest unable to start with hugepage backed memory
+ [Regression]Powerpc kvm guest unable to start with hugepage backed memory

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https://bugs.launchpad.net/bugs/1866962

Title:
  [Regression]Powerpc kvm guest unable to start with hugepage backed
  memory

Status in QEMU:
  New

Bug description:
  Current upstream qemu master does not boot a powerpc kvm guest backed
  by hugepage.

  HW: Power9 (DD2.3)
  Host Kernel: 5.6.0-rc5
  Guest Kernel: 5.6.0-rc5
  Qemu: ba29883206d92a29ad5a466e679ccfc2ee6132ef

  Steps to reproduce:
  1. Allocate enough hugepage to boot a KVM guest
  # cat /proc/meminfo |grep ^HugePages
  HugePages_Total:    5000
  HugePages_Free:     5000
  HugePages_Rsvd:        0
  HugePages_Surp:        0

  2. Define and boot a guest
  /usr/bin/virt-install --connect=qemu:///system --hvm --accelerate --name 
'vm1' --machine pseries --memory=8192,hugepages=yes 
--vcpu=8,maxvcpus=8,sockets=1,cores=8,threads=1 --import --nographics --serial 
pty --memballoon model=virtio --controller type=scsi,model=virtio-scsi --disk 
path=/home/kvmci/tests/data/avocado-vt/images/f31-ppc64le.qcow2,bus=scsi,size=10,format=qcow2
 --network=bridge=virbr0,model=virtio,mac=52:54:00:5f:82:83 
--mac=52:54:00:5f:82:83 --boot 
emulator=/home/sath/qemu/ppc64-softmmu/qemu-system-ppc64,kernel=/home/kvmci/linux/vmlinux,kernel_args="root=/dev/sda5
 rw console=tty0 console=ttyS0,115200 init=/sbin/init initcall_debug selinux=0" 
--noautoconsole

  Starting install...
  ERROR    internal error: qemu unexpectedly closed the monitor: 
qemu-system-ppc64: util/qemu-thread-posix.c:76: qemu_mutex_lock_impl: Assertion 
`mutex->initialized' failed.
  qemu-system-ppc64: util/qemu-thread-posix.c:76: qemu_mutex_lock_impl: 
Assertion `mutex->initialized' failed.

   -----------NOK

  
  Bisected the issue to below commit.

  037fb5eb3941c80a2b7c36a843e47207ddb004d4 is the first bad commit
  commit 037fb5eb3941c80a2b7c36a843e47207ddb004d4
  Author: bauerchen <address@hidden>
  Date:   Tue Feb 11 17:10:35 2020 +0800

      mem-prealloc: optimize large guest startup
      
      [desc]:
          Large memory VM starts slowly when using -mem-prealloc, and
          there are some areas to optimize in current method;
      
          1、mmap will be used to alloc threads stack during create page
          clearing threads, and it will attempt mm->mmap_sem for write
          lock, but clearing threads have hold read lock, this competition
          will cause threads createion very slow;
      
          2、methods of calcuating pages for per threads is not well;if we use
          64 threads to split 160 hugepage,63 threads clear 2page,1 thread
          clear 34 page,so the entire speed is very slow;
      
          to solve the first problem,we add a mutex in thread function,and
          start all threads when all threads finished createion;
          and the second problem, we spread remainder to other threads,in
          situation that 160 hugepage and 64 threads, there are 32 threads
          clear 3 pages,and 32 threads clear 2 pages.
      
      [test]:
          320G 84c VM start time can be reduced to 10s
          680G 84c VM start time can be reduced to 18s
      
      Signed-off-by: bauerchen <address@hidden>
      Reviewed-by: Pan Rui <address@hidden>
      Reviewed-by: Ivan Ren <address@hidden>
      [Simplify computation of the number of pages per thread. - Paolo]
      Signed-off-by: Paolo Bonzini <address@hidden>

   util/oslib-posix.c | 32 ++++++++++++++++++++++++--------
   1 file changed, 24 insertions(+), 8 deletions(-)


  bisect log:

  # git bisect log
  git bisect start
  # good: [52901abf94477b400cf88c1f70bb305e690ba2de] Update version for 
v4.2.0-rc5 release
  git bisect good 52901abf94477b400cf88c1f70bb305e690ba2de
  # bad: [ba29883206d92a29ad5a466e679ccfc2ee6132ef] Merge remote-tracking 
branch 'remotes/borntraeger/tags/s390x-20200310' into staging
  git bisect bad ba29883206d92a29ad5a466e679ccfc2ee6132ef
  # good: [d1ebbc9d16297b54b153ee33abe05eb4f1df0c66] target/arm/kvm: trivial: 
Clean up header documentation
  git bisect good d1ebbc9d16297b54b153ee33abe05eb4f1df0c66
  # good: [87b74e8b6edd287ea2160caa0ebea725fa8f1ca1] target/arm: Vectorize USHL 
and SSHL
  git bisect good 87b74e8b6edd287ea2160caa0ebea725fa8f1ca1
  # bad: [e0175b71638cf4398903c0d25f93fe62e0606389] Merge remote-tracking 
branch 'remotes/pmaydell/tags/pull-target-arm-20200228' into staging
  git bisect bad e0175b71638cf4398903c0d25f93fe62e0606389
  # bad: [ca6155c0f2bd39b4b4162533be401c98bd960820] Merge tag 
'patchew/address@hidden' of https://github.com/patchew-project/qemu into HEAD
  git bisect bad ca6155c0f2bd39b4b4162533be401c98bd960820
  # good: [ab74e543112957696f7c79b0c33ecebd18b52af5] ppc/spapr: use memdev for 
RAM
  git bisect good ab74e543112957696f7c79b0c33ecebd18b52af5
  # good: [cb06fdad05f3e546a4e20f1f3c0127f9ae53de1a] fuzz: support for 
fork-based fuzzing.
  git bisect good cb06fdad05f3e546a4e20f1f3c0127f9ae53de1a
  # bad: [037fb5eb3941c80a2b7c36a843e47207ddb004d4] mem-prealloc: optimize 
large guest startup
  git bisect bad 037fb5eb3941c80a2b7c36a843e47207ddb004d4
  # good: [88e2b97aa3e369a454c9d8360afddc348070c708] Merge remote-tracking 
branch 'remotes/dgilbert-gitlab/tags/pull-virtiofs-20200221' into staging
  git bisect good 88e2b97aa3e369a454c9d8360afddc348070c708
  # good: [b1db8c63169f2139af9f26c884e5e2abd27dd290] fuzz: add virtio-net fuzz 
target
  git bisect good b1db8c63169f2139af9f26c884e5e2abd27dd290
  # good: [e5c59355ae9f724777c61c859292ec9db2c8c2ab] fuzz: add documentation to 
docs/devel/
  git bisect good e5c59355ae9f724777c61c859292ec9db2c8c2ab
  # good: [920d557e5ae58671d335acbcfba3f9a97a02911c] memory: batch allocate 
ioeventfds[] in address_space_update_ioeventfds()
  git bisect good 920d557e5ae58671d335acbcfba3f9a97a02911c
  # first bad commit: [037fb5eb3941c80a2b7c36a843e47207ddb004d4] mem-prealloc: 
optimize large guest startup


  
  Qemu cmdline:
  ```
  /home/sath/qemu/ppc64-softmmu/qemu-system-ppc64 \
  -name guest=vm1,debug-threads=on \
  -S \
  -object 
secret,id=masterKey0,format=raw,file=/var/lib/libvirt/qemu/domain-9-vm1/master-key.aes
 \
  -machine pseries-5.0,accel=kvm,usb=off,dump-guest-core=off \
  -m 8192 \
  -mem-prealloc \
  -mem-path /dev/hugepages/libvirt/qemu/9-vm1 \
  -overcommit mem-lock=off \
  -smp 8,sockets=1,cores=8,threads=1 \
  -uuid e5875dd8-0d1c-422f-ae46-9a0b88919902 \
  -display none \
  -no-user-config \
  -nodefaults \
  -chardev socket,id=charmonitor,fd=36,server,nowait \
  -mon chardev=charmonitor,id=monitor,mode=control \
  -rtc base=utc \
  -no-shutdown \
  -boot strict=on \
  -kernel /home/kvmci/linux/vmlinux \
  -append 'root=/dev/sda5 rw console=tty0 console=ttyS0,115200 init=/sbin/init 
initcall_debug selinux=0' \
  -device qemu-xhci,p2=15,p3=15,id=usb,bus=pci.0,addr=0x3 \
  -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x2 \
  -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x4 \
  -drive 
file=/home/kvmci/tests/data/avocado-vt/images/f31-ppc64le.qcow2,format=qcow2,if=none,id=drive-scsi0-0-0-0
 \
  -device 
scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,device_id=drive-scsi0-0-0-0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0,bootindex=1
 \
  -netdev tap,fd=38,id=hostnet0,vhost=on,vhostfd=39 \
  -device 
virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:5f:82:83,bus=pci.0,addr=0x1 
\
  -chardev pty,id=charserial0 \
  -device spapr-vty,chardev=charserial0,id=serial0,reg=0x30000000 \
  -chardev socket,id=charchannel0,fd=40,server,nowait \
  -device 
virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0
 \
  -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 \
  -msg timestamp=on
  2020-03-11 08:11:46.639+0000: 494632: info : libvirt version: 5.6.0, package: 
5.fc31 (Fedora Project, 2019-11-11-20:24:40, )
  2020-03-11 08:11:46.639+0000: 494632: info : hostname: 
ltcmihawk50.aus.stglabs.ibm.com
  2020-03-11 08:11:46.639+0000: 494632: info : virObjectUnref:349 : 
OBJECT_UNREF: obj=0x7fff3c0f6fb0
  char device redirected to /dev/pts/2 (label charserial0)
  qemu-system-ppc64: util/qemu-thread-posix.c:76: qemu_mutex_lock_impl: 
Assertion `mutex->initialized' failed.
  qemu-system-ppc64: util/qemu-thread-posix.c:76: qemu_mutex_lock_impl: 
Assertion `mutex->initialized' failed.
  2020-03-11 08:11:47.195+0000: shutting down, reason=failed
  ```

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