s390/mm: support EDAT2 for gmap shadows

If the guest is enabled for EDAT2, we can easily create shadows for
guest2 -> guest3 provided tables that make use of EDAT2.

If guest2 references a 2GB page, this memory looks consecutive for guest2,
but it does not have to be so for us. Therefore we have to create fake
segment and page tables.

This works just like EDAT1 support, so page tables are removed when the
parent table (r3t table entry) is changed.

We don't hve to care about:
- ACCF-Validity Control in RTTE
- Access-Control Bits in RTTE
- Fetch-Protection Bit in RTTE
- Common-Region Bit in RTTE

Just like for EDAT1, all bits might be dropped and there is no guaranteed
that they are active.

Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 20 insertions, 2 deletions

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index af1fc6fa7b74..fab03ecb5bd5 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1042,17 +1042,35 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
 			return PGM_REGION_THIRD_TRANS;
 		if (rtte.tt != TABLE_TYPE_REGION3)
 			return PGM_TRANSLATION_SPEC;
+		if (rtte.cr && asce.p && sg->edat_level >= 2)
+			return PGM_TRANSLATION_SPEC;
+		if (rtte.fc && sg->edat_level >= 2) {
+			bool prot = rtte.fc1.p;
+
+			*fake = 1;
+			ptr = rtte.fc1.rfaa << 31UL;
+			rtte.val = ptr;
+			rtte.fc0.p = prot;
+			goto shadow_sgt;
+		}
 		if (vaddr.sx01 < rtte.fc0.tf || vaddr.sx01 > rtte.fc0.tl)
 			return PGM_SEGMENT_TRANSLATION;
-		rc = gmap_shadow_sgt(sg, saddr, rtte.val);
+		ptr = rtte.fc0.sto << 12UL;
+shadow_sgt:
+		rc = gmap_shadow_sgt(sg, saddr, rtte.val, *fake);
 		if (rc)
 			return rc;
-		ptr = rtte.fc0.sto * 4096;
 		/* fallthrough */
 	}
 	case ASCE_TYPE_SEGMENT: {
 		union segment_table_entry ste;
 
+		if (*fake) {
+			/* offset in 2G guest memory block */
+			ptr = ptr + ((unsigned long) vaddr.sx << 20UL);
+			ste.val = ptr;
+			goto shadow_pgt;
+		}
 		rc = gmap_read_table(parent, ptr + vaddr.sx * 8, &ste.val);
 		if (rc)
 			return rc;