Re: [PATCH v2 07/13] s390x: protvirt: SCLP interpretation

[David Hildenbrand]

On 29.11.19 10:48, Janosch Frank wrote:
> SCLP for a protected guest is done over the SIDAD, so we need to use
> the s390_cpu_virt_mem_* functions to access the SIDAD instead of guest
> memory when reading/writing SCBs.

... Can you elaborate a bit more how that is going to be used? Did you
hack in special memory access to something called "SIDAD" via
s390_cpu_virt_mem_*?

I'd suggest a different access path ... especially because

a) it's confusing
b) it's unclear how exceptions apply

...

> 
> To not confuse the sclp emulation, we set 0x4000 as the SCCB address,
> since the function that injects the sclp external interrupt would
> reject a zero sccb address.
> 
> Signed-off-by: Janosch Frank <address@hidden>
> ---
>  hw/s390x/sclp.c         | 17 +++++++++++++++++
>  include/hw/s390x/sclp.h |  2 ++
>  target/s390x/kvm.c      |  5 +++++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
> index f57ce7b739..ca71ace664 100644
> --- a/hw/s390x/sclp.c
> +++ b/hw/s390x/sclp.c
> @@ -193,6 +193,23 @@ static void sclp_execute(SCLPDevice *sclp, SCCB *sccb, 
> uint32_t code)
>      }
>  }
>  
> +#define SCLP_PV_DUMMY_ADDR 0x4000
> +int sclp_service_call_protected(CPUS390XState *env, uint64_t sccb,
> +                                uint32_t code)
> +{
> +    SCLPDevice *sclp = get_sclp_device();
> +    SCLPDeviceClass *sclp_c = SCLP_GET_CLASS(sclp);
> +    SCCB work_sccb;
> +    hwaddr sccb_len = sizeof(SCCB);
> +
> +    s390_cpu_virt_mem_read(env_archcpu(env), 0, 0, &work_sccb, sccb_len);
> +    sclp_c->execute(sclp, &work_sccb, code);
> +    s390_cpu_virt_mem_write(env_archcpu(env), 0, 0, &work_sccb,
> +                            be16_to_cpu(work_sccb.h.length));

this access itself without handling exceptions looks dangerous as it is
completely unclear what's happening here.

> +    sclp_c->service_interrupt(sclp, SCLP_PV_DUMMY_ADDR);
> +    return 0;
> +}
> +
>  int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code)
>  {
>      SCLPDevice *sclp = get_sclp_device();
> diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
> index c54413b78c..c0a3faa37d 100644
> --- a/include/hw/s390x/sclp.h
> +++ b/include/hw/s390x/sclp.h
> @@ -217,5 +217,7 @@ void s390_sclp_init(void);
>  void sclp_service_interrupt(uint32_t sccb);
>  void raise_irq_cpu_hotplug(void);
>  int sclp_service_call(CPUS390XState *env, uint64_t sccb, uint32_t code);
> +int sclp_service_call_protected(CPUS390XState *env, uint64_t sccb,
> +                                uint32_t code);
>  
>  #endif
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index 3d9c44ba9d..b802d02ff5 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -1174,6 +1174,11 @@ static void kvm_sclp_service_call(S390CPU *cpu, struct 
> kvm_run *run,
>      sccb = env->regs[ipbh0 & 0xf];
>      code = env->regs[(ipbh0 & 0xf0) >> 4];
>  
> +    if (run->s390_sieic.icptcode == ICPT_PV_INSTR) {

isn't checking against env->pv easier and cleaner?


-- 
Thanks,

David / dhildenb