Re: [PATCH v7 08/17] target/s390x: Support AES XTS for cpacf km instruction

[Harald Freudenberger <freude@linux.ibm.com>]

On 2026-06-18 07:45, Finn Callies wrote:
> On 17.06.26 11:48, Harald Freudenberger wrote:
>> Support the subfunctions XTS-AES-128 and XTS-AES-256
>> for the cpacf km instruction.
>> 
>> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
>> Tested-by: Holger Dengler <dengler@linux.ibm.com>
>> ---
>>   target/s390x/gen-features.c      |   2 +
>>   target/s390x/tcg/cpacf.h         |   4 ++
>>   target/s390x/tcg/cpacf_aes.c     | 107 
>> +++++++++++++++++++++++++++++++
>>   target/s390x/tcg/crypto_helper.c |   6 ++
>>   4 files changed, 119 insertions(+)
> 
> [ snip ]
> 
>> +
>> +    /* process up to MAX_BLOCKS_PER_RUN aes blocks */
>> +    for (i = 0; i < MAX_BLOCKS_PER_RUN && len >= AES_BLOCK_SIZE; i++) 
>> {
> 
> I guess this has the same "feature" as the real xts where the pcc part
> is not included if not explicitly done beforehand by the user right?
> But since CPACF does it that way I guess you can't do it the "correct"
> way. Instead of XTS + PCC you could implement Full XTS... just
> something to think about.
> 
>> +        /* fetch one AES block into buf1  */
>> +        aes_read_block(env, mmu_idx, *src_ptr_reg + done, buf1, ra);
>> +        /* buf1 xor tweak => buf2 */
> 
> [ snip ]

Well Finn, it is a CPACF emulation - not an emulation about what CPACF
should return if it would have been designed the right way :-)