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

[Christian Borntraeger]

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.