Hi Eric,
I just successfully tested this kunit test on kernel tag next-20260602
and qemu master HEAD == 405c32d2b18a("Merge tag 'pull-tpm-2026-06-01-1'
of https://github.com/stefanberger/qemu-tpm into staging") [1]
If you are using Qemu >= v10.0.0 then the kunit test failure you
reported is due to Qemu not enabling 'cap-nested-papr' capability which
is needed to enable KVM-HV Apiv2 support in Qemu.
Without 'cap-nested-papr' Qemu doesnt register the H_GUEST_GET_STATE
Hcall which this kunit test relies on. Hence it returns -2 (H_FUNCTION)
for this unsupported HCall. The failure of kunit 'test_gs_hostwide_msg'
is expected as the underlying hypervisor doesnt have support nested-papr
APIv2 capability.
To fix this please enable qemu-system-ppc64 machine's capability
cap-nested-papr to enable nested-papr APIv2 support.
Below is the test log showing successful 'guest_state_buffer_test' kunit
test passing :
$ ./qemu-system-ppc64 --version
QEMU emulator version 11.0.50 (v11.0.0-1621-g405c32d2b1)
Copyright (c) 2003-2026 Fabrice Bellard and the QEMU Project developers
# kunit test is specific to nested-papr APIv2 so qemu cap-nested-papr needs to
be enabled
$ ./qemu-system-ppc64 -display none -nographic -kernel ~/linux/vmlinux
-machine pseries,cap-nested-papr=true
<snip>
Booting from memory...
OF stdout device is: /vdevice/vty@71000000
Preparing to boot Linux version 7.1.0-rc6-next-20260602 (vaibhav@*********)
(gcc (GCC) 16.1.1 20260515 (Red Hat 16.1.1-2), GNU ld version 2.46-3.fc44) #2
SMP PREEMPT Wed Jun 3 04:11:38 CDT 2026
Detected machine type: 0000000000000101
<snip>
[ 4.335850][ T1] KTAP version 1
[ 4.335896][ T1] # Subtest: guest_state_buffer_test
[ 4.335946][ T1] # module: test_guest_state_buffer
[ 4.335970][ T1] 1..7
[ 4.337296][ T1] ok 1 test_creating_buffer
[ 4.338998][ T1] ok 2 test_adding_element
[ 4.341996][ T1] ok 3 test_gs_bitmap
[ 4.343406][ T1] ok 4 test_gs_parsing
[ 4.345607][ T1] ok 5 test_gs_msg
[ 4.347247][ T1] ok 6 test_gs_hostwide_msg
[ 4.348012][ T131] # test_gs_hostwide_counters: Guest Heap Size=0 bytes
[ 4.348183][ T131] # test_gs_hostwide_counters: Guest Heap Size Max=0
bytes
[ 4.348350][ T131] # test_gs_hostwide_counters: Guest Page-table Size=0
bytes
[ 4.348653][ T131] # test_gs_hostwide_counters: Guest Page-table Size
Max=0 bytes
[ 4.348813][ T131] # test_gs_hostwide_counters: Guest Page-table
Reclaim Size=0 bytes
[ 4.349354][ T1] ok 7 test_gs_hostwide_counters
[ 4.349569][ T1] # guest_state_buffer_test: pass:7 fail:0 skip:0 total:7
[ 4.349635][ T1] # Totals: pass:7 fail:0 skip:0 total:7
[ 4.349708][ T1] ok 4 guest_state_buffer_test
Can you try adding 'cap-nested-papr=true' to the Qemu machine you are
using and see if the problem resolves for you. If it persists can you
please share the Qemu command line you are using.
[1]
https://gitlab.com/qemu-project/qemu/-/commit/405c32d2b18a683ba36301351af75125d9afda08
Eric Biggers <[email protected]> writes:
> On Wed, Jun 03, 2026 at 01:03:09PM +0530, Vaibhav Jain wrote:
>> Hi Eric,
>>
>> Thanks for trying and reporting this. This kunit test depends on
>> availablility of Qemu commit 5f7d861e("spapr: nested: Add support for
>> reporting Hostwide state counter ") [1] that was merged in v10.0.0.
>>
>> Since you havent mentioned the qemu version used I assume its a version
>> < v10.0.0 . With the qemu patch available you should see this test
>> passing with results similar to as originally described in original
>> cover letter of the patch series at [2] that introduced this kunit test.
>>
>> [1]
>> https://gitlab.com/qemu-project/qemu/-/commit/5f7d861e65d90e0446b8f22a0bc859a5d8058ea6
>>
>> [2] https://lore.kernel.org/all/[email protected]/
>
> Nope, it fails even on the master branch of QEMU.
>
> - Eric
--
Cheers
~ Vaibhav
