s390/mm: support real-space for gmap shadows

We can easily support real-space designation just like EDAT1 and EDAT2.
So guest2 can provide for guest3 an asce with the real-space control being
set.

We simply have to allocate the biggest page table possible and fake all
levels.

There is no protection to consider. If we exceed guest memory, vsie code
will inject an addressing exception (via program intercept). In the future,
we could limit the fake table level to the gmap page table.

As the top level page table can never go away, such gmap shadows will never
get unshadowed, we'll have to come up with another way to limit the number
of kept gmap shadows.

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, 29 insertions, 5 deletions

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index f6d556dfafcd..54200208bf24 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -971,9 +971,13 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
         vaddr.addr = saddr;
         asce.val = sg->orig_asce;
         ptr = asce.origin * 4096;
+        if (asce.r) {
+                *fake = 1;
+                asce.dt = ASCE_TYPE_REGION1;
+        }
         switch (asce.dt) {
         case ASCE_TYPE_REGION1:
-                if (vaddr.rfx01 > asce.tl)
+                if (vaddr.rfx01 > asce.tl && !asce.r)
                         return PGM_REGION_FIRST_TRANS;
                 break;
         case ASCE_TYPE_REGION2:
@@ -1000,6 +1004,12 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
         case ASCE_TYPE_REGION1: {
                 union region1_table_entry rfte;
 
+                if (*fake) {
+                        /* offset in 16EB guest memory block */
+                        ptr = ptr + ((unsigned long) vaddr.rsx << 53UL);
+                        rfte.val = ptr;
+                        goto shadow_r2t;
+                }
                 rc = gmap_read_table(parent, ptr + vaddr.rfx * 8, &rfte.val);
                 if (rc)
                         return rc;
@@ -1011,15 +1021,22 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
                         return PGM_REGION_SECOND_TRANS;
                 if (sg->edat_level >= 1)
                         *dat_protection |= rfte.p;
-                rc = gmap_shadow_r2t(sg, saddr, rfte.val);
+                ptr = rfte.rto << 12UL;
+shadow_r2t:
+                rc = gmap_shadow_r2t(sg, saddr, rfte.val, *fake);
                 if (rc)
                         return rc;
-                ptr = rfte.rto * 4096;
                 /* fallthrough */
         }
         case ASCE_TYPE_REGION2: {
                 union region2_table_entry rste;
 
+                if (*fake) {
+                        /* offset in 8PB guest memory block */
+                        ptr = ptr + ((unsigned long) vaddr.rtx << 42UL);
+                        rste.val = ptr;
+                        goto shadow_r3t;
+                }
                 rc = gmap_read_table(parent, ptr + vaddr.rsx * 8, &rste.val);
                 if (rc)
                         return rc;
@@ -1031,16 +1048,23 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
                         return PGM_REGION_THIRD_TRANS;
                 if (sg->edat_level >= 1)
                         *dat_protection |= rste.p;
+                ptr = rste.rto << 12UL;
+shadow_r3t:
                 rste.p |= *dat_protection;
-                rc = gmap_shadow_r3t(sg, saddr, rste.val);
+                rc = gmap_shadow_r3t(sg, saddr, rste.val, *fake);
                 if (rc)
                         return rc;
-                ptr = rste.rto * 4096;
                 /* fallthrough */
         }
         case ASCE_TYPE_REGION3: {
                 union region3_table_entry rtte;
 
+                if (*fake) {
+                        /* offset in 4TB guest memory block */
+                        ptr = ptr + ((unsigned long) vaddr.sx << 31UL);
+                        rtte.val = ptr;
+                        goto shadow_sgt;
+                }
                 rc = gmap_read_table(parent, ptr + vaddr.rtx * 8, &rtte.val);
                 if (rc)
                         return rc;