s390/mm: extended gmap pte notifier
The current gmap pte notifier forces a pte into to a read-write state.
If the pte is invalidated the gmap notifier is called to inform KVM
that the mapping will go away.
Extend this approach to allow read-write, read-only and no-access
as possible target states and call the pte notifier for any change
to the pte.
This mechanism is used to temporarily set specific access rights for
a pte without doing the heavy work of a true mprotect call.
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 8b56423..480c076 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -553,29 +553,29 @@
static DEFINE_SPINLOCK(gmap_notifier_lock);
/**
- * gmap_register_ipte_notifier - register a pte invalidation callback
+ * gmap_register_pte_notifier - register a pte invalidation callback
* @nb: pointer to the gmap notifier block
*/
-void gmap_register_ipte_notifier(struct gmap_notifier *nb)
+void gmap_register_pte_notifier(struct gmap_notifier *nb)
{
spin_lock(&gmap_notifier_lock);
list_add_rcu(&nb->list, &gmap_notifier_list);
spin_unlock(&gmap_notifier_lock);
}
-EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);
+EXPORT_SYMBOL_GPL(gmap_register_pte_notifier);
/**
- * gmap_unregister_ipte_notifier - remove a pte invalidation callback
+ * gmap_unregister_pte_notifier - remove a pte invalidation callback
* @nb: pointer to the gmap notifier block
*/
-void gmap_unregister_ipte_notifier(struct gmap_notifier *nb)
+void gmap_unregister_pte_notifier(struct gmap_notifier *nb)
{
spin_lock(&gmap_notifier_lock);
list_del_rcu(&nb->list);
spin_unlock(&gmap_notifier_lock);
synchronize_rcu();
}
-EXPORT_SYMBOL_GPL(gmap_unregister_ipte_notifier);
+EXPORT_SYMBOL_GPL(gmap_unregister_pte_notifier);
/**
* gmap_call_notifier - call all registered invalidation callbacks
@@ -593,62 +593,150 @@
}
/**
- * gmap_ipte_notify - mark a range of ptes for invalidation notification
+ * gmap_table_walk - walk the gmap page tables
+ * @gmap: pointer to guest mapping meta data structure
+ * @gaddr: virtual address in the guest address space
+ *
+ * Returns a table pointer for the given guest address.
+ */
+static inline unsigned long *gmap_table_walk(struct gmap *gmap,
+ unsigned long gaddr)
+{
+ unsigned long *table;
+
+ table = gmap->table;
+ switch (gmap->asce & _ASCE_TYPE_MASK) {
+ case _ASCE_TYPE_REGION1:
+ table += (gaddr >> 53) & 0x7ff;
+ if (*table & _REGION_ENTRY_INVALID)
+ return NULL;
+ table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+ /* Fallthrough */
+ case _ASCE_TYPE_REGION2:
+ table += (gaddr >> 42) & 0x7ff;
+ if (*table & _REGION_ENTRY_INVALID)
+ return NULL;
+ table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+ /* Fallthrough */
+ case _ASCE_TYPE_REGION3:
+ table += (gaddr >> 31) & 0x7ff;
+ if (*table & _REGION_ENTRY_INVALID)
+ return NULL;
+ table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
+ /* Fallthrough */
+ case _ASCE_TYPE_SEGMENT:
+ table += (gaddr >> 20) & 0x7ff;
+ }
+ return table;
+}
+
+/**
+ * gmap_pte_op_walk - walk the gmap page table, get the page table lock
+ * and return the pte pointer
+ * @gmap: pointer to guest mapping meta data structure
+ * @gaddr: virtual address in the guest address space
+ * @ptl: pointer to the spinlock pointer
+ *
+ * Returns a pointer to the locked pte for a guest address, or NULL
+ */
+static pte_t *gmap_pte_op_walk(struct gmap *gmap, unsigned long gaddr,
+ spinlock_t **ptl)
+{
+ unsigned long *table;
+
+ /* Walk the gmap page table, lock and get pte pointer */
+ table = gmap_table_walk(gmap, gaddr);
+ if (!table || *table & _SEGMENT_ENTRY_INVALID)
+ return NULL;
+ return pte_alloc_map_lock(gmap->mm, (pmd_t *) table, gaddr, ptl);
+}
+
+/**
+ * gmap_pte_op_fixup - force a page in and connect the gmap page table
+ * @gmap: pointer to guest mapping meta data structure
+ * @gaddr: virtual address in the guest address space
+ * @vmaddr: address in the host process address space
+ *
+ * Returns 0 if the caller can retry __gmap_translate (might fail again),
+ * -ENOMEM if out of memory and -EFAULT if anything goes wrong while fixing
+ * up or connecting the gmap page table.
+ */
+static int gmap_pte_op_fixup(struct gmap *gmap, unsigned long gaddr,
+ unsigned long vmaddr)
+{
+ struct mm_struct *mm = gmap->mm;
+ bool unlocked = false;
+
+ if (fixup_user_fault(current, mm, vmaddr, FAULT_FLAG_WRITE, &unlocked))
+ return -EFAULT;
+ if (unlocked)
+ /* lost mmap_sem, caller has to retry __gmap_translate */
+ return 0;
+ /* Connect the page tables */
+ return __gmap_link(gmap, gaddr, vmaddr);
+}
+
+/**
+ * gmap_pte_op_end - release the page table lock
+ * @ptl: pointer to the spinlock pointer
+ */
+static void gmap_pte_op_end(spinlock_t *ptl)
+{
+ spin_unlock(ptl);
+}
+
+/**
+ * gmap_mprotect_notify - change access rights for a range of ptes and
+ * call the notifier if any pte changes again
* @gmap: pointer to guest mapping meta data structure
* @gaddr: virtual address in the guest address space
* @len: size of area
+ * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
*
- * Returns 0 if for each page in the given range a gmap mapping exists and
- * the invalidation notification could be set. If the gmap mapping is missing
- * for one or more pages -EFAULT is returned. If no memory could be allocated
- * -ENOMEM is returned. This function establishes missing page table entries.
+ * Returns 0 if for each page in the given range a gmap mapping exists,
+ * the new access rights could be set and the notifier could be armed.
+ * If the gmap mapping is missing for one or more pages -EFAULT is
+ * returned. If no memory could be allocated -ENOMEM is returned.
+ * This function establishes missing page table entries.
*/
-int gmap_ipte_notify(struct gmap *gmap, unsigned long gaddr, unsigned long len)
+int gmap_mprotect_notify(struct gmap *gmap, unsigned long gaddr,
+ unsigned long len, int prot)
{
- unsigned long addr;
+ unsigned long vmaddr;
spinlock_t *ptl;
pte_t *ptep;
- bool unlocked;
int rc = 0;
if ((gaddr & ~PAGE_MASK) || (len & ~PAGE_MASK))
return -EINVAL;
+ if (!MACHINE_HAS_ESOP && prot == PROT_READ)
+ return -EINVAL;
down_read(&gmap->mm->mmap_sem);
while (len) {
- unlocked = false;
- /* Convert gmap address and connect the page tables */
- addr = __gmap_translate(gmap, gaddr);
- if (IS_ERR_VALUE(addr)) {
- rc = addr;
- break;
+ rc = -EAGAIN;
+ ptep = gmap_pte_op_walk(gmap, gaddr, &ptl);
+ if (ptep) {
+ rc = ptep_force_prot(gmap->mm, gaddr, ptep, prot);
+ gmap_pte_op_end(ptl);
}
- /* Get the page mapped */
- if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE,
- &unlocked)) {
- rc = -EFAULT;
- break;
- }
- /* While trying to map mmap_sem got unlocked. Let us retry */
- if (unlocked)
+ if (rc) {
+ vmaddr = __gmap_translate(gmap, gaddr);
+ if (IS_ERR_VALUE(vmaddr)) {
+ rc = vmaddr;
+ break;
+ }
+ rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr);
+ if (rc)
+ break;
continue;
- rc = __gmap_link(gmap, gaddr, addr);
- if (rc)
- break;
- /* Walk the process page table, lock and get pte pointer */
- ptep = get_locked_pte(gmap->mm, addr, &ptl);
- VM_BUG_ON(!ptep);
- /* Set notification bit in the pgste of the pte */
- if ((pte_val(*ptep) & (_PAGE_INVALID | _PAGE_PROTECT)) == 0) {
- ptep_set_notify(gmap->mm, addr, ptep);
- gaddr += PAGE_SIZE;
- len -= PAGE_SIZE;
}
- pte_unmap_unlock(ptep, ptl);
+ gaddr += PAGE_SIZE;
+ len -= PAGE_SIZE;
}
up_read(&gmap->mm->mmap_sem);
return rc;
}
-EXPORT_SYMBOL_GPL(gmap_ipte_notify);
+EXPORT_SYMBOL_GPL(gmap_mprotect_notify);
/**
* ptep_notify - call all invalidation callbacks for a specific pte.
