Re: [Qemu-devel] [PATCH-for-4.2 v1 9/9] s390x/cpumodel: Add new TCG features to QEMU cpu model

[Cornelia Huck <cohuck@redhat.com>]

On Mon,  5 Aug 2019 17:29:47 +0200
David Hildenbrand <david@redhat.com> wrote:

> We now implement a bunch of new facilities we can properly indicate.
> 
> ESOP-1/ESOP-2 handling is discussed in the PoP Chafter 3-15
> ("Suppression on Protection"). The "Basic suppression-on-protection (SOP)
> facility" is a core part of z/Architecture without a facility
> indication. ESOP-2 is indicated by ESOP-1 + Side-effect facility
> ("ESOP-2"). Besides ESOP-2, the side-effect facility is only relevant for
> the guarded-storage facility (we don't implement).
> 
> S390_ESOP:
> - We indicate DAT exeptions by setting bit 61 of the TEID (TEC) to 1 and
>   bit 60 to zero. We don't trigger ALCP exceptions yet. Also, we set
>   bit 0-51 and bit 62/63 to the right values.
> S390_ACCESS_EXCEPTION_FS_INDICATION:
> - The TEID (TEC) properly indicates in bit 52/53 on any access if it was
>   a fetch or a store
> S390_SIDE_EFFECT_ACCESS_ESOP2:
> - We have no side-effect accesses (esp., we don't implement the
>   guarded-storage faciliy), we correctly set bit 64 of the TEID (TEC) to
>   0 (no side-effect).
> - ESOP2: We properly set bit 56, 60, 61 in the TEID (TEC) to indicate the
>   type of protection. We don't trigger KCP/ALCP exceptions yet.
> S390_INSTRUCTION_EXEC_PROT:
> - The MMU properly detects and indicates the exception on instruction fetches
> - Protected TLB entries will never get PAGE_EXEC set.
> 
> There is no need to fake the abscence of any of the facilities - without
> the facilities, some bits of the TEID (TEC) are simply unpredictable.
> 
> As IEP was added with z14 and we currently implement a z13, add it to
> the MAX model instead.

Looks sane, once we get those features supported.

> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/gen-features.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target/s390x/gen-features.c b/target/s390x/gen-features.c
> index 7e82f2f004..6e78d40d9a 100644
> --- a/target/s390x/gen-features.c
> +++ b/target/s390x/gen-features.c
> @@ -704,12 +704,16 @@ static uint16_t qemu_V4_1[] = {
>  };
>  
>  static uint16_t qemu_LATEST[] = {
> +    S390_FEAT_ACCESS_EXCEPTION_FS_INDICATION,
> +    S390_FEAT_SIDE_EFFECT_ACCESS_ESOP2,
> +    S390_FEAT_ESOP,
>  };
>  
>  /* add all new definitions before this point */
>  static uint16_t qemu_MAX[] = {
>      /* generates a dependency warning, leave it out for now */
>      S390_FEAT_MSA_EXT_5,
> +    S390_FEAT_INSTRUCTION_EXEC_PROT,

This 'dependency warning' only refers to msa_ext_5, no? Can we make
that more obvious?

>  };
>  
>  /****** END FEATURE DEFS ******/