memory in ubuntu_kvm_unit_tests fails (clflushopt / clwb ABSENT)

[Po-Hsu Lin]

 FAIL: clflushopt (ABSENT)
 FAIL: clwb (ABSENT)

Test output:

Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/memory'
 BUILD_HEAD=32db322d
 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.SOyUkPCNxP -smp 1 -cpu max # -initrd /tmp/tmp.DiAWwvk2jC
 enabling apic
 PASS: clflush (present)
 PASS: sfence (present)
 PASS: lfence (present)
 PASS: mfence (present)
 FAIL: clflushopt (ABSENT)
 FAIL: clwb (ABSENT)
 PASS: invalid clwb
 PASS: pcommit (ABSENT)
 SUMMARY: 8 tests, 2 unexpected failures
 FAIL memory (8 tests, 2 unexpected failures)

[Po-Hsu Lin (cypressyew)]

Passed with Oracle Bionic 4.15

[Po-Hsu Lin (cypressyew)]

Oops, spoke too soon.

This has passed with Oracle Bionic 4.15 on VM.DenseIO1.8, but failed on VM.DenseIO2.16

[Po-Hsu Lin (cypressyew)]

Passed on VM.DenseIO1.8 and VM.Standard1.4 for Oracle B-4.15

[Sean Feole (sfeole)]

see the same sort of failure on E-linux-kvm

12/09 11:58:32 DEBUG| utils:0116| Running 'kvm-ok'
12/09 11:58:32 DEBUG| utils:0153| [stdout] INFO: /dev/kvm exists
12/09 11:58:32 DEBUG| utils:0153| [stdout] KVM acceleration can be used
12/09 11:58:32 DEBUG| utils:0116| Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/memory'
12/09 11:58:32 DEBUG| utils:0153| [stdout] BUILD_HEAD=e2c275c4
12/09 11:58:32 DEBUG| utils:0153| [stdout] timeout -k 1s --foreground 90s /usr/bin/qemu-system-x86_64 -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.YNkf1n3ucP -smp 1 -cpu host # -initrd /tmp/tmp.6LT1XGulTr
12/09 11:58:33 DEBUG| utils:0153| [stdout] enabling apic
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: clflush (present)
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: sfence (present)
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: lfence (present)
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: mfence (present)
12/09 11:58:33 DEBUG| utils:0153| [stdout] FAIL: clflushopt (ABSENT)
12/09 11:58:33 DEBUG| utils:0153| [stdout] FAIL: clwb (ABSENT)
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: invalid clwb
12/09 11:58:33 DEBUG| utils:0153| [stdout] PASS: pcommit (ABSENT)
12/09 11:58:33 DEBUG| utils:0153| [stdout] SUMMARY: 8 tests, 2 unexpected failures
12/09 11:58:33 DEBUG| utils:0153| [stdout] FAIL memory (8 tests, 2 unexpected failures)
12/09 11:58:33 ERROR| test:0414| Exception escaping from test:

[Po-Hsu Lin (cypressyew)]

With 4.15.0-1037.41 Oracle
Failed with VM.Standard2.16
Passed with VM.Standard2.1

[Kelsey Steele (kelsey-steele)]

failed on Bionic/azure-4.15 : 4.15.0-1097.107 : amd64

[Kelsey Steele (kelsey-steele)]

Failed on Bionic/oracle : 5.4.0-1026.26~18.04.1 : amd64

[Francis Ginther (fginther)]

Seen with linux-oracle 4.15.0-1065.73~16.04.1.

[Po-Hsu Lin (cypressyew)]

Found on 5.11.0-1009.9+21.10.1-kvm

 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.RiE0Ijtuov -smp 1 -cpu max # -initrd /tmp/tmp.G3a4COl6Lh
 enabling apic
 PASS: clflush (present)
 PASS: sfence (present)
 PASS: lfence (present)
 PASS: mfence (present)
 FAIL: clflushopt (ABSENT)
 FAIL: clwb (ABSENT)
 PASS: invalid clwb
 PASS: pcommit (ABSENT)
 SUMMARY: 8 tests, 2 unexpected failures
 FAIL memory (8 tests, 2 unexpected failures)

[Guilherme G. Piccoli (gpiccoli)]

Observed in H/KVM, cycle sru-20210531.

[Guilherme G. Piccoli (gpiccoli)]

Observed in G/KVM, cycle sru-20210531.

[Guilherme G. Piccoli (gpiccoli)]

Observed in F/KVM, cycle sru-20210531.

[Guilherme G. Piccoli (gpiccoli)]

Observed in B/KVM, cycle sru-20210531.

[Guilherme G. Piccoli (gpiccoli)]

Observed in T-4.15/Azure, cycle sru-20210531.

[Po-Hsu Lin (cypressyew)]

Found on H-kvm 5.11.0-1015.16

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Po-Hsu Lin (cypressyew)]

When comparing the Focal 5.4 generic AMD64 kernel test output and Focal 5.4 KVM AMD64 kernel test output, you can see the generic kernel will pass with:

 PASS: clflush (present)
 PASS: sfence (present)
 PASS: lfence (present)
 PASS: mfence (present)
 PASS: clflushopt (ABSENT)
 PASS: clwb (ABSENT)
 PASS: invalid clwb
 PASS: pcommit (ABSENT)
 SUMMARY: 8 tests
 PASS memory (8 tests)

Instead the KVM kernel will fail with:
 FAIL: clflushopt (ABSENT)
 FAIL: clwb (ABSENT)

I wonder what's the difference here.