KVM: s390: Clear storage keys

page_table_reset_pgste() already does a complete page table walk to
reset the pgste. Enhance it to initialize the storage keys to
PAGE_DEFAULT_KEY if requested by the caller. This will be used
for lazy storage key handling. Also provide an empty stub for
!CONFIG_PGSTE

Lets adopt the current code (diag 308) to not clear the keys.
Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

arch/s390/include/asm/pgalloc.h

@@ -22,7 +22,8 @@ unsigned long *page_table_alloc(struct mm_struct *, unsigned long);
 void page_table_free(struct mm_struct *, unsigned long *);
 void page_table_free_rcu(struct mmu_gather *, unsigned long *);
 
-void page_table_reset_pgste(struct mm_struct *, unsigned long, unsigned long);
+void page_table_reset_pgste(struct mm_struct *, unsigned long, unsigned long,
+			    bool init_skey);
 int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 			  unsigned long key, bool nq);
 

arch/s390/kvm/diag.c

@@ -169,15 +169,15 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
 	switch (subcode) {
 	case 0:
 	case 1:
-		page_table_reset_pgste(current->mm, 0, TASK_SIZE);
+		page_table_reset_pgste(current->mm, 0, TASK_SIZE, false);
 		return -EOPNOTSUPP;
 	case 3:
 		vcpu->run->s390_reset_flags = KVM_S390_RESET_CLEAR;
-		page_table_reset_pgste(current->mm, 0, TASK_SIZE);
+		page_table_reset_pgste(current->mm, 0, TASK_SIZE, false);
 		break;
 	case 4:
 		vcpu->run->s390_reset_flags = 0;
-		page_table_reset_pgste(current->mm, 0, TASK_SIZE);
+		page_table_reset_pgste(current->mm, 0, TASK_SIZE, false);
 		break;
 	default:
 		return -EOPNOTSUPP;

arch/s390/mm/pgtable.c

@@ -883,8 +883,8 @@ static inline void page_table_free_pgste(unsigned long *table)
 	__free_page(page);
 }
 
-static inline unsigned long page_table_reset_pte(struct mm_struct *mm,
-			pmd_t *pmd, unsigned long addr, unsigned long end)
+static inline unsigned long page_table_reset_pte(struct mm_struct *mm, pmd_t *pmd,
+			unsigned long addr, unsigned long end, bool init_skey)
 {
 	pte_t *start_pte, *pte;
 	spinlock_t *ptl;
@@ -895,6 +895,22 @@ static inline unsigned long page_table_reset_pte(struct mm_struct *mm,
 	do {
 		pgste = pgste_get_lock(pte);
 		pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK;
+		if (init_skey) {
+			unsigned long address;
+
+			pgste_val(pgste) &= ~(PGSTE_ACC_BITS | PGSTE_FP_BIT |
+					      PGSTE_GR_BIT | PGSTE_GC_BIT);
+
+			/* skip invalid and not writable pages */
+			if (pte_val(*pte) & _PAGE_INVALID ||
+			    !(pte_val(*pte) & _PAGE_WRITE)) {
+				pgste_set_unlock(pte, pgste);
+				continue;
+			}
+
+			address = pte_val(*pte) & PAGE_MASK;
+			page_set_storage_key(address, PAGE_DEFAULT_KEY, 1);
+		}
 		pgste_set_unlock(pte, pgste);
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 	pte_unmap_unlock(start_pte, ptl);
@@ -902,8 +918,8 @@ static inline unsigned long page_table_reset_pte(struct mm_struct *mm,
 	return addr;
 }
 
-static inline unsigned long page_table_reset_pmd(struct mm_struct *mm,
-			pud_t *pud, unsigned long addr, unsigned long end)
+static inline unsigned long page_table_reset_pmd(struct mm_struct *mm, pud_t *pud,
+			unsigned long addr, unsigned long end, bool init_skey)
 {
 	unsigned long next;
 	pmd_t *pmd;
@@ -913,14 +929,14 @@ static inline unsigned long page_table_reset_pmd(struct mm_struct *mm,
 		next = pmd_addr_end(addr, end);
 		if (pmd_none_or_clear_bad(pmd))
 			continue;
-		next = page_table_reset_pte(mm, pmd, addr, next);
+		next = page_table_reset_pte(mm, pmd, addr, next, init_skey);
 	} while (pmd++, addr = next, addr != end);
 
 	return addr;
 }
 
-static inline unsigned long page_table_reset_pud(struct mm_struct *mm,
-			pgd_t *pgd, unsigned long addr, unsigned long end)
+static inline unsigned long page_table_reset_pud(struct mm_struct *mm, pgd_t *pgd,
+			unsigned long addr, unsigned long end, bool init_skey)
 {
 	unsigned long next;
 	pud_t *pud;
@@ -930,14 +946,14 @@ static inline unsigned long page_table_reset_pud(struct mm_struct *mm,
 		next = pud_addr_end(addr, end);
 		if (pud_none_or_clear_bad(pud))
 			continue;
-		next = page_table_reset_pmd(mm, pud, addr, next);
+		next = page_table_reset_pmd(mm, pud, addr, next, init_skey);
 	} while (pud++, addr = next, addr != end);
 
 	return addr;
 }
 
-void page_table_reset_pgste(struct mm_struct *mm,
-			unsigned long start, unsigned long end)
+void page_table_reset_pgste(struct mm_struct *mm, unsigned long start,
+			    unsigned long end, bool init_skey)
 {
 	unsigned long addr, next;
 	pgd_t *pgd;
@@ -949,7 +965,7 @@ void page_table_reset_pgste(struct mm_struct *mm,
 		next = pgd_addr_end(addr, end);
 		if (pgd_none_or_clear_bad(pgd))
 			continue;
-		next = page_table_reset_pud(mm, pgd, addr, next);
+		next = page_table_reset_pud(mm, pgd, addr, next, init_skey);
 	} while (pgd++, addr = next, addr != end);
 	up_read(&mm->mmap_sem);
 }
@@ -1011,6 +1027,11 @@ static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
 	return NULL;
 }
 
+void page_table_reset_pgste(struct mm_struct *mm, unsigned long start,
+			    unsigned long end, bool init_skey)
+{
+}
+
 static inline void page_table_free_pgste(unsigned long *table)
 {
 }