ACK: [SRU][N][J][PATCH 0/1] s390/cpum_cf: make crypto counters upward compatible (LP: 2074380)

[Andrei Gherzan]

On 24/08/01 12:53pm, frank.heimes at canonical.com wrote:
> BugLink: https://bugs.launchpad.net/bugs/2074380
> 
> SRU Justification:
> 
> [ Impact ]
> 
>  * The CPU Measurement Facility (CPU MF) crypto counter set
>    is not listed in the device sysfs tree - it's not exported
>    in the sysfs directory /sys/devices/cpum_cf/events.
> 
>  * The attribute files for each CPU-MF counter defined
>    in the crypto counter set is missing.
> 
>  * This is caused by the counter second version number of CPU MF
>    hardware being incremented on new machines.
> 
>  * This causes a sanity check to fail,
>    but the counters are supported by hardware.
> 
>  * The solution is to remove the upper limit in counter second
>    version number check.
> 
> [ Fix ]
> 
>  * f10933cbd2df f10933cbd2dfddf6273698a45f76db9bafd8150f
>    "s390/cpum_cf: make crypto counters upward compatible across machine types"
> 
>  * The fix was upstream accepted with kernel v6.10(-rc1).
> 
>  * Upstream commit applies cleanly on noble master-next,
>    but needed to be backported to jammy master-next due to different code
>    and context in kernel 5.15.
> 
> [ Test Plan ]
> 
>  * Run the following commands on a new machine generation:
>    (hence only doable by IBM)
>    # ls -l /sys/devices/cpum_cf/events/ | grep AES
> 
>  * If the output is empty than this patch is required.
> 
>  * With a patched kernel the output should be like:
>    # ls /sys/devices/cpum_cf/events/ | grep AES
>    AES_BLOCKED_CYCLES
>    AES_BLOCKED_FUNCTIONS
>    AES_CYCLES
>    AES_FUNCTIONS
> 
> [ Where problems could occur ]
> 
>  * This affects s390x only - CPU MF is s390-specific,
>    and only s390 specific code is modified.
> 
>  * And it furthermore is limited to the crypto counter set
>    of CPU MF.
> 
>  * So any impact is likely limited to hardware crypto counters
>    on s390x only.
> 
>  * In s390/kernel/perf_cpum_cf.c the else if case got changed from
>    explicitly checking for 6 or 7 to >= 6 which seems to require
>    attention for future 8 and more cases.
> 
>  * In s390/kernel/perf_cpum_cf_events.c the switch (ci.csvn) statement
>    was changed to an if / else if with similar logic.
>    Again attentioin for any potential future cases >= 8.
> 
>  * It does not look like currently used cases (1..5 and 6..7)
>    are affected by the modification, just >7.
> 
>  * Test build of patched jammy and noble s390x kernels were build
>    and are avaiable here:
>    https://launchpad.net/~fheimes/+archive/ubuntu/lp2074380
> 
> [ Other Info ]
> 
>  * Since the code/fix was upstream accepted with kernel v6.10(-rc1)
>    it does not affect the current development release oracular.
> 
>  * This SRU can also be seen under the umbrella of new
>     hardware enablement.
> 
>  * Since it requires special hw, the verification needs to be
>    done by IBM.
> 
> Thomas Richter (1):
>   s390/cpum_cf: make crypto counters upward compatible across machine
>     types
> 
>  arch/s390/kernel/perf_cpum_cf.c        |  2 +-
>  arch/s390/kernel/perf_cpum_cf_events.c | 11 +++--------

Acked-by: Andrei Gherzan <andrei.gherzan at canonical.com>

-- 
Andrei Gherzan
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