From: David Hildenbrand <da...@redhat.com> STFL bit 4 and 5 are just indications to the guest, which TLB entries an IDTE call will clear. These are performance indicators for the guest.
STFL bit 4: INVALIDATE DAT TABLE ENTRY (IDTE) performs the invalidation-and-clearing operation by selectively clearing TLB segment-table entries when a segment-table entry or entries are invalidated. IDTE also performs the clearing-by- ASCE operation. Unless bit 4 is one, IDTE simply purges all TLBs. Bit 3 is one if bit 4 is one. We can simply set STFL bit 4 ("idtes") and still purge the complete TLB. Purging more than advertised is never bad. E.g. Linux doesn't even care about this bit. We can optimized this later. This is helpful, as the z9 base model contains this facility. STFL bit 5 (clearing TLB region-table-entries) was never implemented on real HW, therefore we can simply ignore it for now. Signed-off-by: David Hildenbrand <da...@redhat.com> Message-Id: <20170627161032.5014-1-da...@redhat.com> Signed-off-by: Richard Henderson <r...@twiddle.net> --- target/s390x/cpu_models.c | 1 + 1 file changed, 1 insertion(+) diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c index 91ef8eb..ca9168d 100644 --- a/target/s390x/cpu_models.c +++ b/target/s390x/cpu_models.c @@ -676,6 +676,7 @@ static void add_qemu_cpu_model_features(S390FeatBitmap fbm) { static const int feats[] = { S390_FEAT_DAT_ENH, + S390_FEAT_IDTE_SEGMENT, S390_FEAT_STFLE, S390_FEAT_EXTENDED_IMMEDIATE, S390_FEAT_EXTENDED_TRANSLATION_2, -- 2.9.4