Re: [Qemu-devel] [PULL 35/40] s390x/cpumodel: we are always in zarchitecture mode

[David Hildenbrand]

On 14.07.2017 12:41, Christian Borntraeger wrote:
> From: "Jason J. Herne" <address@hidden>
> 
> In QEMU, a guest VCPU always started in and never was able to leave
> z/Architecture mode. Now we have an architected way of showing this
> condition.
> 
> The SIGP SET ARCHITECTURE instruction is simply rejected. Linux as guest
> seems to not care about the return value, which is a good thing
> The new handling is just like already being in z/Architecture mode.
> 
> We'll not try to fake absence of this facility, but still not indicate
> the facility in case some strange CPU model turned z/Architecture off
> completely (which doesn't work either way but let's us see how a
> guest would react on a lack of this facility).
> 
> Signed-off-by: Jason J. Herne <address@hidden>
> Acked-by: Christian Borntraeger <address@hidden>
> Acked-by: Cornelia Huck <address@hidden>
> Signed-off-by: Christian Borntraeger <address@hidden>
> ---
>  target/s390x/cpu_features.c |  5 +++--
>  target/s390x/kvm.c          | 38 +++++++++++---------------------------
>  2 files changed, 14 insertions(+), 29 deletions(-)
> 
> diff --git a/target/s390x/cpu_features.c b/target/s390x/cpu_features.c
> index e5a3f71..fa887d9 100644
> --- a/target/s390x/cpu_features.c
> +++ b/target/s390x/cpu_features.c
> @@ -337,8 +337,9 @@ void s390_fill_feat_block(const S390FeatBitmap features, 
> S390FeatType type,
>      int bit_nr;
>  
>      if (type == S390_FEAT_TYPE_STFL && test_bit(S390_FEAT_ZARCH, features)) {
> -        /* z/Architecture is always active if around */
> -        data[0] |= 0x20;
> +        /* Features that are always active */
> +        data[0] |= 0x20;  /* z/Architecture */
> +        data[17] |= 0x20; /* Configuration-z-architectural-mode */
>      }

This also requires changes in TCG , no? (set architecture there is left
untouched)


-- 

Thanks,

David