Re: [Qemu-devel] [PATCH v1] s390x/tcg: fix loading 31bit PSWs with the highest bit set

[Thomas Huth <thuth@redhat.com>]

On 01.03.2018 13:08, David Hildenbrand wrote:
> Let's also put the 31-bit hack in front of the REAL MMU, otherwise right
> now we get errors when loading a PSW where the highest bit is set (e.g.
> via s390-netboot.img). The highest bit is not masked away, therefore we
> inject addressing exceptions into the guest.
> 
> The proper fix will later be to do all address wrapping before accessing
> the MMU - so we won't get any "wrong" entries in there (which makes
> flushing also easier). But that will require more work (wrapping in
> load_psw, wrapping when incrementing the PC, wrapping every memory
> access).
> 
> This fixes the tests/pxe-test test.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  target/s390x/excp_helper.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c
> index 411051edc3..dfee221111 100644
> --- a/target/s390x/excp_helper.c
> +++ b/target/s390x/excp_helper.c
> @@ -107,6 +107,10 @@ int s390_cpu_handle_mmu_fault(CPUState *cs, vaddr orig_vaddr, int size,
>              return 1;
>          }
>      } else if (mmu_idx == MMU_REAL_IDX) {
> +        /* 31-Bit mode */
> +        if (!(env->psw.mask & PSW_MASK_64)) {
> +            vaddr &= 0x7fffffff;
> +        }

Since the preceeding if-statement has exactly the same check, I think
you could also merge the two checks by putting that in front of the
if-statement instead?

Apart from that, patch looks good to me.

 Thomas