[PATCH v4 7/9] s390/mm: Add huge pmd storage key handling

[Janosch Frank <frankja@xxxxxxxxxxxxx>]

From: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>

Storage keys for guests with huge page mappings have to directly set
the key in hardware. There are no PGSTEs for PMDs that we could use to
retain the guests's logical view of the key.

As pmds are handled from userspace side, KVM skey emulation for split
pmds will always use the hardware's storage key.

Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxxxxxxx>
---
 arch/s390/mm/pgtable.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 98 insertions(+), 6 deletions(-)

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 7bc79aae3c25..158c880226fe 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -811,12 +811,45 @@ EXPORT_SYMBOL_GPL(test_and_clear_guest_dirty);
 int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 			  unsigned char key, bool nq)
 {
-	unsigned long keyul;
+	unsigned long keyul, address;
 	spinlock_t *ptl;
 	pgste_t old, new;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
 	pte_t *ptep;
 
-	ptep = get_locked_pte(mm, addr, &ptl);
+	pgd = pgd_offset(mm, addr);
+	p4d = p4d_alloc(mm, pgd, addr);
+	if (!p4d)
+		return -EFAULT;
+	pud = pud_alloc(mm, p4d, addr);
+	if (!pud)
+		return -EFAULT;
+	pmd = pmd_alloc(mm, pud, addr);
+	if (!pmd)
+		return -EFAULT;
+
+	ptl = pmd_lock(mm, pmd);
+	if (!pmd_present(*pmd)) {
+		spin_unlock(ptl);
+		return -EFAULT;
+	}
+	if (pmd_large(*pmd)) {
+		address = pmd_val(*pmd) & HPAGE_MASK;
+		address |= addr & ~HPAGE_MASK;
+		/*
+		 * Huge pmds need quiescing operations, they are
+		 * always mapped.
+		 */
+		page_set_storage_key(address, key, 1);
+		spin_unlock(ptl);
+		return 0;
+	}
+	spin_unlock(ptl);
+
+	ptep = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (unlikely(!ptep))
 		return -EFAULT;
 
@@ -827,7 +860,7 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 	pgste_val(new) |= (keyul & (_PAGE_CHANGED | _PAGE_REFERENCED)) << 48;
 	pgste_val(new) |= (keyul & (_PAGE_ACC_BITS | _PAGE_FP_BIT)) << 56;
 	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
-		unsigned long address, bits, skey;
+		unsigned long bits, skey;
 
 		address = pte_val(*ptep) & PAGE_MASK;
 		skey = (unsigned long) page_get_storage_key(address);
@@ -890,14 +923,43 @@ EXPORT_SYMBOL(cond_set_guest_storage_key);
 int reset_guest_reference_bit(struct mm_struct *mm, unsigned long addr)
 {
 	spinlock_t *ptl;
+	unsigned long address;
 	pgste_t old, new;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
 	pte_t *ptep;
 	int cc = 0;
 
-	ptep = get_locked_pte(mm, addr, &ptl);
-	if (unlikely(!ptep))
+	pgd = pgd_offset(mm, addr);
+	p4d = p4d_alloc(mm, pgd, addr);
+	if (!p4d)
+		return -EFAULT;
+	pud = pud_alloc(mm, p4d, addr);
+	if (!pud)
+		return -EFAULT;
+	pmd = pmd_alloc(mm, pud, addr);
+	if (!pmd)
 		return -EFAULT;
 
+	ptl = pmd_lock(mm, pmd);
+	if (!pmd_present(*pmd)) {
+		spin_unlock(ptl);
+		return -EFAULT;
+	}
+	if (pmd_large(*pmd)) {
+		address = pmd_val(*pmd) & HPAGE_MASK;
+		address |= addr & ~HPAGE_MASK;
+		cc = page_reset_referenced(addr);
+		spin_unlock(ptl);
+		return cc;
+	}
+	spin_unlock(ptl);
+
+	ptep = pte_alloc_map_lock(mm, pmd, addr, &ptl);
+	if (unlikely(!ptep))
+		return -EFAULT;
 	new = old = pgste_get_lock(ptep);
 	/* Reset guest reference bit only */
 	pgste_val(new) &= ~PGSTE_GR_BIT;
@@ -922,11 +984,41 @@ EXPORT_SYMBOL(reset_guest_reference_bit);
 int get_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 			  unsigned char *key)
 {
+	unsigned long address;
 	spinlock_t *ptl;
 	pgste_t pgste;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
 	pte_t *ptep;
 
-	ptep = get_locked_pte(mm, addr, &ptl);
+	pgd = pgd_offset(mm, addr);
+	p4d = p4d_alloc(mm, pgd, addr);
+	if (!p4d)
+		return -EFAULT;
+	pud = pud_alloc(mm, p4d, addr);
+	if (!pud)
+		return -EFAULT;
+	pmd = pmd_alloc(mm, pud, addr);
+	if (!pmd)
+		return -EFAULT;
+
+	ptl = pmd_lock(mm, pmd);
+	if (!pmd_present(*pmd)) {
+		spin_unlock(ptl);
+		return -EFAULT;
+	}
+	if (pmd_large(*pmd)) {
+		address = pmd_val(*pmd) & HPAGE_MASK;
+		address |= addr & ~HPAGE_MASK;
+		*key = page_get_storage_key(address);
+		spin_unlock(ptl);
+		return 0;
+	}
+	spin_unlock(ptl);
+
+	ptep = pte_alloc_map_lock(mm, pmd, addr, &ptl);
 	if (unlikely(!ptep))
 		return -EFAULT;
 
-- 
2.14.3