Re: [PATCH v3] target/s390x: support PRNO_TRNG instruction

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 02.08.22 um 15:54 schrieb David Hildenbrand:
> On 02.08.22 15:26, Christian Borntraeger wrote:
>>
>>
>> Am 20.07.22 um 14:08 schrieb Jason A. Donenfeld:
>>> In order for hosts running inside of TCG to initialize the kernel's
>>> random number generator, we should support the PRNO_TRNG instruction,
>>> backed in the usual way with the qemu_guest_getrandom helper. This is
>>> confirmed working on Linux 5.19-rc6.
>>>
>>> Cc: Thomas Huth <thuth@redhat.com>
>>> Cc: David Hildenbrand <david@redhat.com>
>>> Cc: Richard Henderson <richard.henderson@linaro.org>
>>> Cc: Cornelia Huck <cohuck@redhat.com>
>>> Cc: Harald Freudenberger <freude@linux.ibm.com>
>>> Cc: Holger Dengler <dengler@linux.ibm.com>
>>> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
>> [...]
>>> +    case 114:
>>> +        if (r1 & 1 || !r1 || r2 & 1 || !r2)
>>> +                tcg_s390_program_interrupt(env, PGM_SPECIFICATION, ra);
>>> +        fill_buf_random(env, ra, &env->regs[r1], &env->regs[r1 + 1]);
>>> +        fill_buf_random(env, ra, &env->regs[r2], &env->regs[r2 + 1]);
>>> +        break;
>>
>> I think I agree with Harald that some aspects are missing.
>> Linux does not seem to check, but we should also modify the query function to
>> indicate the availability of 114.
>>
>> As the msa helper deals with many instructions
>> ...
>> target/s390x/tcg/insn-data.def:    D(0xb91e, KMAC,    RRE,   MSA,  0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMAC)
>> target/s390x/tcg/insn-data.def:    D(0xb928, PCKMO,   RRE,   MSA3, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_PCKMO)
>> target/s390x/tcg/insn-data.def:    D(0xb92a, KMF,     RRE,   MSA4, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMF)
>> target/s390x/tcg/insn-data.def:    D(0xb92b, KMO,     RRE,   MSA4, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMO)
>> target/s390x/tcg/insn-data.def:    D(0xb92c, PCC,     RRE,   MSA4, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_PCC)
>> target/s390x/tcg/insn-data.def:    D(0xb92d, KMCTR,   RRF_b, MSA4, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMCTR)
>> target/s390x/tcg/insn-data.def:    D(0xb92e, KM,      RRE,   MSA,  0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KM)
>> target/s390x/tcg/insn-data.def:    D(0xb92f, KMC,     RRE,   MSA,  0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMC)
>> target/s390x/tcg/insn-data.def:    D(0xb929, KMA,     RRF_b, MSA8, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KMA)
>> target/s390x/tcg/insn-data.def:    D(0xb93c, PPNO,    RRE,   MSA5, 0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_PPNO)
>> target/s390x/tcg/insn-data.def:    D(0xb93e, KIMD,    RRE,   MSA,  0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KIMD)
>> target/s390x/tcg/insn-data.def:    D(0xb93f, KLMD,    RRE,   MSA,  0, 0, 0, 0, msa, 0, S390_FEAT_TYPE_KLMD)
>> ...
>> and in theory other instructions might also have 114 we should at least check that this is ppno/prno.
>> Or we split out a prno helper from the msa helper.
>>
> 
> Doesn't
> 
> s390_get_feat_block(type, subfunc);
> if (!test_be_bit(fc, subfunc)) {
> 	tcg_s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> }
> 
> check that? As long as we don't implement 114 for any other instruction.
> that should properly fence off the other instructions.

Right that would help. We should still take care of the query function.