KVM: s390: handle missing storage-key facility

Without the storage-key facility, SIE won't interpret SSKE, ISKE and
RRBE for us. So let's add proper interception handlers that will be called
if lazy sske cannot be enabled.

Reviewed-by: Christian Borntraeger <borntraeger@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, 37 insertions, 0 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index e791e8b27fd2..fa286d0c0f2d 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -572,6 +572,43 @@ int cond_set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL(cond_set_guest_storage_key);
 
+/**
+ * Reset a guest reference bit (rrbe), returning the reference and changed bit.
+ *
+ * Returns < 0 in case of error, otherwise the cc to be reported to the guest.
+ */
+int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr)
+{
+	spinlock_t *ptl;
+	pgste_t old, new;
+	pte_t *ptep;
+	int cc = 0;
+
+	ptep = get_locked_pte(mm, addr, &ptl);
+	if (unlikely(!ptep))
+		return -EFAULT;
+
+	new = old = pgste_get_lock(ptep);
+	/* Reset guest reference bit only */
+	pgste_val(new) &= ~PGSTE_GR_BIT;
+
+	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
+		cc = page_reset_referenced(pte_val(*ptep) & PAGE_MASK);
+		/* Merge real referenced bit into host-set */
+		pgste_val(new) |= ((unsigned long) cc << 53) & PGSTE_HR_BIT;
+	}
+	/* Reflect guest's logical view, not physical */
+	cc |= (pgste_val(old) & (PGSTE_GR_BIT | PGSTE_GC_BIT)) >> 49;
+	/* Changing the guest storage key is considered a change of the page */
+	if ((pgste_val(new) ^ pgste_val(old)) & PGSTE_GR_BIT)
+		pgste_val(new) |= PGSTE_UC_BIT;
+
+	pgste_set_unlock(ptep, new);
+	pte_unmap_unlock(ptep, ptl);
+	return 0;
+}
+EXPORT_SYMBOL(reset_guest_reference_bit);
+
 int get_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 			  unsigned char *key)
 {