Re: [PATCH v9 08/10] target/s390x: interception of PTF instruction

[Janis Schoetterl-Glausch]

On Fri, 2022-09-02 at 09:55 +0200, Pierre Morel wrote:
> When the host supports the CPU topology facility, the PTF
> instruction with function code 2 is interpreted by the SIE,
> provided that the userland hypervizor activates the interpretation
> by using the KVM_CAP_S390_CPU_TOPOLOGY KVM extension.
> 
> The PTF instructions with function code 0 and 1 are intercepted
> and must be emulated by the userland hypervizor.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>

Reviewed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>

See note below.
> ---
>  hw/s390x/cpu-topology.c            | 52 ++++++++++++++++++++++++++++++
>  include/hw/s390x/s390-virtio-ccw.h |  6 ++++
>  target/s390x/kvm/kvm.c             | 13 ++++++++
>  3 files changed, 71 insertions(+)
> 
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> index b6bf839e40..7dcaa28ca3 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -20,6 +20,58 @@
>  #include "hw/s390x/s390-virtio-ccw.h"
>  #include "hw/s390x/cpu-topology.h"
>  #include "migration/vmstate.h"
> +#include "target/s390x/cpu.h"
> +#include "hw/s390x/s390-virtio-ccw.h"
> +
> +/*
> + * s390_handle_ptf:
> + *
> + * @register 1: contains the function code
> + *
> + * Function codes 0 and 1 handle the CPU polarization.
> + * We assume an horizontal topology, the only one supported currently
> + * by Linux, consequently we answer to function code 0, requesting
> + * horizontal polarization that it is already the current polarization
> + * and reject vertical polarization request without further explanation.
> + *
> + * Function code 2 is handling topology changes and is interpreted
> + * by the SIE.
> + */
> +void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
> +{
> +    CPUS390XState *env = &cpu->env;
> +    uint64_t reg = env->regs[r1];
> +    uint8_t fc = reg & S390_TOPO_FC_MASK;
> +
> +    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
> +        s390_program_interrupt(env, PGM_OPERATION, ra);
> +        return;

I'm either expecting this function to return -1 here...
> +    }
> +
> +    if (env->psw.mask & PSW_MASK_PSTATE) {
> +        s390_program_interrupt(env, PGM_PRIVILEGED, ra);
> +        return;
> +    }
> +
> +    if (reg & ~S390_TOPO_FC_MASK) {
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +        return;
> +    }
> +
> +    switch (fc) {
> +    case 0:    /* Horizontal polarization is already set */
> +        env->regs[r1] |= S390_PTF_REASON_DONE;
> +        setcc(cpu, 2);
> +        break;
> +    case 1:    /* Vertical polarization is not supported */
> +        env->regs[r1] |= S390_PTF_REASON_NONE;
> +        setcc(cpu, 2);
> +        break;
> +    default:
> +        /* Note that fc == 2 is interpreted by the SIE */
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +    }
> +}

[...]
>  
> +static int kvm_handle_ptf(S390CPU *cpu, struct kvm_run *run)
> +{
> +    uint8_t r1 = (run->s390_sieic.ipb >> 20) & 0x0f;
> +
> +    s390_handle_ptf(cpu, r1, RA_IGNORED);

... and this being returned here...
> +
> +    return 0;

... or this function being void.
> +}
> +
>  static int handle_b9(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1)
>  {
>      int r = 0;
> @@ -1480,6 +1490,9 @@ static int handle_b9(S390CPU *cpu, struct kvm_run *run, 
> uint8_t ipa1)
>      case PRIV_B9_RPCIT:
>          r = kvm_rpcit_service_call(cpu, run);
>          break;
> +    case PRIV_B9_PTF:
> +        r = kvm_handle_ptf(cpu, run);
> +        break;
>      case PRIV_B9_EQBS:
>          /* just inject exception */
>          r = -1;