On 2017-06-23 01:12, David Hildenbrand wrote:
> If we have for example: r3 contains 0x00000000ffffffff
> ec 33 3f bf 61 55 risbg %r3,%r3,63,191,97
>
> We want to rotate 33 to the left and only keep MSB bit 63 of that. So the
> result is then exactly 1 (we're reading the sign of the 32 bit value).
>
> Current code assumes that we can do that via an extract, which is not
> true (at least not that easy) and produces a 0.
I think the mistake there is that the rotation is done to the left,
while in extract the "shift" is done to the right. The following patch
should be enough:
--- a/target/s390x/translate.c
+++ b/target/s390x/translate.c
@@ -3441,8 +3441,8 @@ static ExitStatus op_risbg(DisasContext *s, DisasOps *o)
}
/* In some cases we can implement this with extract. */
- if (imask == 0 && pos == 0 && len > 0 && rot + len <= 64) {
- tcg_gen_extract_i64(o->out, o->in2, rot, len);
+ if (imask == 0 && pos == 0 && len > 0 && rot - len >= 0) {
+ tcg_gen_extract_i64(o->out, o->in2, 64 - rot, len);
return NO_EXIT;
> Let's just get rid of this special handling.
>
> Signed-off-by: David Hildenbrand <da...@redhat.com>
> ---
>
> This effectively allows to start a linux kernel, compiled for z10 using
> the qemu model under tcg (with other patches currently on the list):
>
> qemu-system-s390x ... -cpu qemu,mvcos=on,stfle=on,ldisp=on,ldisphp=on, \
> eimm=on,stckf=on,csst=on,csst2=on,ginste=on, \
> exrl=on ...
>
> I found this by compiling the kvm-unit-tests for z10 and noticing
> elementary selftests failing. The kernel would trigger weird
> BUG_ONs very early while starting up, which basically gave not really
> many hints of what was actually going wrong.
>
> target/s390x/translate.c | 6 ------
> 1 file changed, 6 deletions(-)
But the patch is also correct.
Reviewed-by: Aurelien Jarno <aurel...@aurel32.net>
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurel...@aurel32.net http://www.aurel32.net
