Re: [PATCH v2 0/2] KVM: s390: fix ESSA addressing exception injection in migration mode

[Claudio Imbrenda]

On Thu, 15 Oct 2026 12:48:20 +0200
Gautam Gala <ggala@xxxxxxxxxxxxx> wrote:

> ESSA emulation in migration mode silently dropped addressing exceptions
> when the guest page-table walk failed, so the guest never received the
> expected PGM_ADDRESSING interrupt during live migration.
> 
> Patch 1 fixes dat_perform_essa() to return PGM_ADDRESSING on a walk 
> failure, and __do_essa() to inject the program interrupt when it sees 
> that return value.
> 
> Patch 2 adds a regression test integrated into the existing cmma_test
> selftest.

Whole series:

Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

> 
> Changes since v1:
>  - dat_perform_essa() now returns +PGM_ADDRESSING instead of
>    -PGM_ADDRESSING; kvm_s390_inject_program_int() takes an unsigned u16
>    so passing -5 would have wrapped to 0xFFFB and injected a bogus PIC.
>    __do_essa() comparison and inject call updated accordingly. The
>    kernel-doc return-value entry is corrected to %PGM_ADDRESSING.
>  - Selftest: pgm_handler_c() now reads the actual PIC from lowcore
>    (__LC_PGM_INT_CODE) instead of hard-coding PGM_ADDRESSING, so the
>    test would have caught the sign error above had it been in v1.
>  - Selftest: virt_map(vm, 0, 0, 1) added so the DAT-on guest can
>    access the lowcore to read the PIC.
>  - Selftest: PGM_ADDRESSING, __LC_PGM_INT_CODE and __LC_PGM_NEW_PSW
>    constants moved to the shared s390/processor.h header.
>  - Selftest: SIGALRM/alarm() timeout wrapper removed.
> 
> Gautam Gala (2):
>   KVM: s390: fix ESSA addressing exception injection in migration mode
>   KVM: s390: selftests: add ESSA migration mode PGM_ADDRESSING
>     regression test
> 
>  arch/s390/kvm/gmap/dat.c                      |  5 +-
>  arch/s390/kvm/s390/priv.c                     |  2 +
>  .../selftests/kvm/include/s390/processor.h    |  7 ++
>  tools/testing/selftests/kvm/s390/cmma_test.c  | 69 +++++++++++++++++++
>  4 files changed, 82 insertions(+), 1 deletion(-)
>