Re: [PATCH v2 06/13] s390x: protvirt: KVM intercept changes

[Cornelia Huck <cohuck@redhat.com>]

On Fri, 29 Nov 2019 04:48:02 -0500
Janosch Frank <frankja@linux.ibm.com> wrote:

> Secure guests no longer intercept with code 4 for an instruction
> interception. Instead they have codes 104 and 108 for secure
> instruction interception and secure instruction notification
> respectively.
> 
> The 104 mirrors the 4 interception.
> 
> The 108 is a notification interception to let KVM and QEMU know that
> something changed and we need to update tracking information or
> perform specific tasks. It's currently taken for the following
> instructions:
> 
> * stpx (To inform about the changed prefix location)
> * sclp (On incorrect SCCB values, so we can inject a IRQ)
> * sigp (All but "stop and store status")
> * diag308 (Subcodes 0/1)
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  target/s390x/kvm.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index ad6e38c876..3d9c44ba9d 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -115,6 +115,8 @@
>  #define ICPT_CPU_STOP                   0x28
>  #define ICPT_OPEREXC                    0x2c
>  #define ICPT_IO                         0x40
> +#define ICPT_PV_INSTR                   0x68
> +#define ICPT_PV_INSTR_NOTIFICATION      0x6c
>  
>  #define NR_LOCAL_IRQS 32
>  /*
> @@ -151,6 +153,7 @@ static int cap_s390_irq;
>  static int cap_ri;
>  static int cap_gs;
>  static int cap_hpage_1m;
> +static int cap_protvirt;
>  
>  static int active_cmma;
>  
> @@ -342,6 +345,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
>      cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
>      cap_s390_irq = kvm_check_extension(s, KVM_CAP_S390_INJECT_IRQ);
> +    cap_protvirt = kvm_check_extension(s, KVM_CAP_S390_PROTECTED);
>  
>      if (!kvm_check_extension(s, KVM_CAP_S390_GMAP)
>          || !kvm_check_extension(s, KVM_CAP_S390_COW)) {
> @@ -1664,6 +1668,8 @@ static int handle_intercept(S390CPU *cpu)
>              (long)cs->kvm_run->psw_addr);
>      switch (icpt_code) {
>          case ICPT_INSTRUCTION:
> +        case ICPT_PV_INSTR:
> +        case ICPT_PV_INSTR_NOTIFICATION:
>              r = handle_instruction(cpu, run);

I'm still a bit uneasy about going through the same path for both 104
and 108. How does the handler figure out whether it should emulate an
instruction, or just process a notification? Is it guaranteed that a
given instruction is always showing up as either a 104 or a 108, so
that the handler can check the pv state?

[Even if that works, it still feels a bit unclean to me.]

>              break;
>          case ICPT_PROGRAM: