ACK: [SRU][I][F][PATCH v2 0/2] Fix SIGP processing on KVM/s390 (LP: 1962578)

[Kleber Souza]

On 04.03.22 08:22, frank.heimes at canonical.com wrote:
> BugLink: https://bugs.launchpad.net/bugs/1962578
> 
> SRU Justification:
> 
> [Impact]
> 
> * The SIGP processing on KVM/s390x is incorrect and not fully conform to
>    the 'Principles of Operations', the IBM Z architecture definition
>    and documentation.
> 
> * KVM: SIGP RESTART is reporting a CPU state 'stopped' after SIGP RESTART
>    was issued, while it should report a 'busy' condition until the CPU is
>    really started.
> 
> * The fix for this consists of three patches:
>    812de04661c4 "KVM: s390: Clarify SIGP orders versus STOP/RESTART"
>    435d17955519 "KVM: s390: Add a routine for setting userspace CPU state"
>    4563bcad46bf "KVM: s390: Simplify SIGP Set Arch handling"
>    whereas 812de04661c4 already landed via upstream stable,
>    hence only two are left and need to be cherry-picked:
> 
> [Fix]
> 
> * 67cf68b6a5ccac8bc7dfef0a220b59af4c83fd2c 67cf68b6a5cc "KVM: s390: Add a routine for setting userspace CPU state"
> 
> * 8eeba194a32e0f50329354a696baaa2e3d9accc5 8eeba194a32e "KVM: s390: Simplify SIGP Set Arch handling"
> 
> [Test Case]
> 
> * Install an LPAR on IBM Z (z13+) or LinuxONE (Emperor / Rockhopper)
>    with Ubuntu Server 20.04 using kernel standard kernel 5.4.
> 
> * Setup this LPAR as QEMU/KVM host and a focal VM as guest.
> 
> * The test itself is the following unit test:
>    https://lore.kernel.org/r/20220303210425.1693486-1-farman@linux.ibm.com/
> 
> * The test and verification will be done by the IBM Z team.
> 
> [Where problems could occur]
> 
> * A broken patch could harm KVM ioctl on s390x or the (virtual) CPU
>    state control in general.
> 
> * The SIGP handing (on s390x) can become broken, which could lead to
>    incorrect (virtual) CPU states.
> 
> * In worst case KVM can become broken on s390x entirely.
> 
> * The modified code is all s390x specific QEMU/KVM code,
>    no common code is touched.
> 
> [Other]
> 
> * The two remaining patches are upstream since 5.16,
>    the first one already landed in 5.4 via upstream stable bug LP#1959701
>    and in 5.13 via upstream stable bug LP#1960861.
> 
> * The patches already landed in jammy (master-next) based on LP#1959735,
>    hence only SRU to impish and focal is needed.
> 
> * This patches got discussed here:
>    https://lore.kernel.org/all/20211008203112.1979843-2-farman@linux.ibm.com/
> 
> * This not only fixes the SIGP processing, but is also important in terms of
>    long term maintainability.
> 
> v2: fixed typos and text of SRU justification
> 
> Eric Farman (2):
>    KVM: s390: Simplify SIGP Set Arch handling
>    KVM: s390: Add a routine for setting userspace CPU state
> 
>   arch/s390/kvm/kvm-s390.c |  6 +++---
>   arch/s390/kvm/kvm-s390.h |  9 +++++++++
>   arch/s390/kvm/sigp.c     | 14 +-------------
>   3 files changed, 13 insertions(+), 16 deletions(-)
> 

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

Thanks