diff mbox series

[GIT,PULL,07/17] s390/mm: optimize set_guest_storage_key()

Message ID 20211031121104.14764-8-borntraeger@de.ibm.com (mailing list archive)
State New, archived
Headers show
Series [GIT,PULL,01/17] s390/gmap: validate VMA in __gmap_zap() | expand

Commit Message

Christian Borntraeger Oct. 31, 2021, 12:10 p.m. UTC 
From: David Hildenbrand <david@redhat.com>

We already optimize get_guest_storage_key() to assume that if we don't have
a PTE table and don't have a huge page mapped that the storage key is 0.

Similarly, optimize set_guest_storage_key() to simply do nothing in case
the key to set is 0.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20210909162248.14969-9-david@redhat.com
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/mm/pgtable.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index e74cc59dcd67..1c9aeb361f8d 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -792,13 +792,23 @@  int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 	pmd_t *pmdp;
 	pte_t *ptep;
 
-	if (pmd_lookup(mm, addr, &pmdp))
+	/*
+	 * If we don't have a PTE table and if there is no huge page mapped,
+	 * we can ignore attempts to set the key to 0, because it already is 0.
+	 */
+	switch (pmd_lookup(mm, addr, &pmdp)) {
+	case -ENOENT:
+		return key ? -EFAULT : 0;
+	case 0:
+		break;
+	default:
 		return -EFAULT;
+	}
 
 	ptl = pmd_lock(mm, pmdp);
 	if (!pmd_present(*pmdp)) {
 		spin_unlock(ptl);
-		return -EFAULT;
+		return key ? -EFAULT : 0;
 	}
 
 	if (pmd_large(*pmdp)) {