canonical-ubuntu-qa team mailing list archive

[Jürg Häfliger <1968681@xxxxxxxxxxxxxxxxxx>]

** Tags added: kernel-daily-bug

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https://bugs.launchpad.net/bugs/1968681

Title:
  rdpru in ubuntu_kvm_unit_tests failed on B-4.15 node riccioli with
  FAIL: RDPRU raises #UD

Status in ubuntu-kernel-tests:
  Fix Released
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Bionic:
  Fix Released

Bug description:
  [Impact]
  RDPRU, the Read Processor Register instruction of AMD Zen 2 processors
  is used to give access to some processor registers that are typically
  only accessible when the privilege level is zero.

  rdpru test in ubuntu_kvm_unit_tests is to check if the RDPRU instruction
  can be intercepted by the Hypervisor. Without this patchset, this test
  will fail on our AMD Zen 2 system "riccioli" with:
    FAIL: RDPRU raises #UD

  [Fix]
  * fb64f293 x86/cpufeatures: Add feature bit RDPRU on AMD
  * 0cb8410b kvm: svm: Intercept RDPRU

  We have these patches in newer releases already, only Bionic 4.15
  requires this fix. The first patch needs to be backported with some
  context adjustment, the second can be cherry-picked.

  [Test]
  Test kernel can be found here:
  https://people.canonical.com/~phlin/kernel/lp-1968681-rdpru/

  With the patched kernel, this rdpru test will pass on the target AMD
  Zen 2 system.
  $ sudo ./rdpru
  BUILD_HEAD=d6421940
  timeout -k 1s --foreground 90s /usr/bin/qemu-system-x86_64 --no-reboot \ 
  -nodefaults -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 \
  -vnc none -serial stdio -device pci-testdev -machine accel=kvm -kernel \
  /tmp/tmp.XOMVxpyNnl -smp 1 -cpu max # -initrd /tmp/tmp.I2TbGXFiaZ
  enabling apic
  smp: waiting for 0 APs
  PASS: RDPRU raises #UD
  SUMMARY: 1 tests
  PASS rdpru (1 tests)

  And the rdpru flag will be available in cpuinfo:
  $ grep -o rdpru /proc/cpuinfo
  rdpru

  [Where problems could occur]
  This patchset will add a new feature bit RDPRU for AMD Zen 2. We can
  expect to see new issues coming up when using this bit in the future.

  [Original Bug Report]
  Issue found on B-ibm-gt-4.15.0-1116.127
  This can be reproduced with B-4.15.0-175 as well.

  This failure is only visible on this node.

   Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/rdpru'
   BUILD_HEAD=16647354
   timeout -k 1s --foreground 90s /usr/bin/qemu-system-x86_64 --no-reboot -nodefaults -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 -vnc none -serial stdio -device pci-testdev -machine accel=kvm -kernel /tmp/tmp.qGIR5tvTw1 -smp 1 -cpu max # -initrd /tmp/tmp.8JuYRCFRUi
   enabling apic
   FAIL: RDPRU raises #UD
   SUMMARY: 1 tests, 1 unexpected failures
   FAIL rdpru (1 tests, 1 unexpected failures)

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