s390/mm: support EDAT1 for gmap shadows

If the guest is enabled for EDAT1, we can easily create shadows for
guest2 -> guest3 provided tables that make use of EDAT1.

If guest2 references a 1MB page, this memory looks consecutive for guest2,
but it might not be so for us. Therefore we have to create fake page tables.

We can easily add that to our existing infrastructure. The invalidation
mechanism will make sure that fake page tables are removed when the parent
table (sgt table entry) is changed.

As EDAT1 also introduced protection on all page table levels, we have to
also shadow these correctly.

We don't have to care about:
- ACCF-Validity Control in STE
- Access-Control Bits in STE
- Fetch-Protection Bit in STE
- Common-Segment Bit in STE

As all bits might be dropped and there is no guaranteed that they are
active ("unpredictable whether the CPU uses these bits", "may be used").
Without using EDAT1 in the shadow ourselfes (STE-format control == 0),
simply shadowing these bits would not be enough. They would be ignored.

Please note that we are using the "fake" flag to make this look consistent
with further changes (EDAT2, real-space designation support) and don't let
the shadow functions handle fc=1 stes.

In the future, with huge pages in the host, gmap_shadow_pgt() could simply
try to map a huge host page if "fake" is set to one and indicate via return
value that no lower fake tables / shadow ptes are required.

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, 27 insertions, 7 deletions

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index a85bc6c6a098..af1fc6fa7b74 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -953,9 +953,11 @@ int kvm_s390_check_low_addr_prot_real(struct kvm_vcpu *vcpu, unsigned long gra)
  * @sg: pointer to the shadow guest address space structure
  * @saddr: faulting address in the shadow gmap
  * @pgt: pointer to the page table address result
+ * @fake: pgt references contiguous guest memory block, not a pgtable
  */
 static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
-                                  unsigned long *pgt, int *dat_protection)
+                                  unsigned long *pgt, int *dat_protection,
+                                  int *fake)
 {
         struct gmap *parent;
         union asce asce;
@@ -963,6 +965,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
         unsigned long ptr;
         int rc;
 
+        *fake = 0;
         parent = sg->parent;
         vaddr.addr = saddr;
         asce.val = sg->orig_asce;
@@ -1060,10 +1063,20 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
                 if (ste.cs && asce.p)
                         return PGM_TRANSLATION_SPEC;
                 *dat_protection = ste.fc0.p;
-                rc = gmap_shadow_pgt(sg, saddr, ste.val);
+                if (ste.fc && sg->edat_level >= 1) {
+                        bool prot = ste.fc1.p;
+
+                        *fake = 1;
+                        ptr = ste.fc1.sfaa << 20UL;
+                        ste.val = ptr;
+                        ste.fc0.p = prot;
+                        goto shadow_pgt;
+                }
+                ptr = ste.fc0.pto << 11UL;
+shadow_pgt:
+                rc = gmap_shadow_pgt(sg, saddr, ste.val, *fake);
                 if (rc)
                         return rc;
-                ptr = ste.fc0.pto * 2048;
         }
         }
         /* Return the parent address of the page table */
@@ -1089,7 +1102,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
         union vaddress vaddr;
         union page_table_entry pte;
         unsigned long pgt;
-        int dat_protection;
+        int dat_protection, fake;
         int rc;
 
         down_read(&sg->mm->mmap_sem);
@@ -1100,17 +1113,24 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
          */
         ipte_lock(vcpu);
 
-        rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection);
+        rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection, &fake);
         if (rc)
-                rc = kvm_s390_shadow_tables(sg, saddr, &pgt, &dat_protection);
+                rc = kvm_s390_shadow_tables(sg, saddr, &pgt, &dat_protection,
+                                            &fake);
 
         vaddr.addr = saddr;
+        if (fake) {
+                /* offset in 1MB guest memory block */
+                pte.val = pgt + ((unsigned long) vaddr.px << 12UL);
+                goto shadow_page;
+        }
         if (!rc)
                 rc = gmap_read_table(sg->parent, pgt + vaddr.px * 8, &pte.val);
         if (!rc && pte.i)
                 rc = PGM_PAGE_TRANSLATION;
-        if (!rc && (pte.z || pte.co))
+        if (!rc && (pte.z || (pte.co && sg->edat_level < 1)))
                 rc = PGM_TRANSLATION_SPEC;
+shadow_page:
         pte.p |= dat_protection;
         if (!rc)
                 rc = gmap_shadow_page(sg, saddr, __pte(pte.val));