KVM: s390: KVM page table management functions: clear and replace

Add page table management functions to be used for KVM guest (gmap)
page tables.

This patch adds functions to clear, replace or exchange DAT table
entries.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c
index c324a27f379f63ea793a4e3e3640774e1c0cdba6..e38b1a139fbb745b3141d2a0a570949b9d5c004c 100644 (file)
--- a/arch/s390/kvm/dat.c
+++ b/arch/s390/kvm/dat.c
@@ -101,3 +101,118 @@ void dat_free_level(struct crst_table *table, bool owns_ptes)
        }
        dat_free_crst(table);
 }
+
+/**
+ * dat_crstep_xchg() - Exchange a gmap CRSTE with another.
+ * @crstep: Pointer to the CRST entry
+ * @new: Replacement entry.
+ * @gfn: The affected guest address.
+ * @asce: The ASCE of the address space.
+ *
+ * Context: This function is assumed to be called with kvm->mmu_lock held.
+ */
+void dat_crstep_xchg(union crste *crstep, union crste new, gfn_t gfn, union asce asce)
+{
+       if (crstep->h.i) {
+               WRITE_ONCE(*crstep, new);
+               return;
+       } else if (cpu_has_edat2()) {
+               crdte_crste(crstep, *crstep, new, gfn, asce);
+               return;
+       }
+
+       if (machine_has_tlb_guest())
+               idte_crste(crstep, gfn, IDTE_GUEST_ASCE, asce, IDTE_GLOBAL);
+       else
+               idte_crste(crstep, gfn, 0, NULL_ASCE, IDTE_GLOBAL);
+       WRITE_ONCE(*crstep, new);
+}
+
+/**
+ * dat_crstep_xchg_atomic() - Atomically exchange a gmap CRSTE with another.
+ * @crstep: Pointer to the CRST entry.
+ * @old: Expected old value.
+ * @new: Replacement entry.
+ * @gfn: The affected guest address.
+ * @asce: The asce of the address space.
+ *
+ * This function is needed to atomically exchange a CRSTE that potentially
+ * maps a prefix area, without having to invalidate it inbetween.
+ *
+ * Context: This function is assumed to be called with kvm->mmu_lock held.
+ *
+ * Return: %true if the exchange was successful.
+ */
+bool dat_crstep_xchg_atomic(union crste *crstep, union crste old, union crste new, gfn_t gfn,
+                           union asce asce)
+{
+       if (old.h.i)
+               return arch_try_cmpxchg((long *)crstep, &old.val, new.val);
+       if (cpu_has_edat2())
+               return crdte_crste(crstep, old, new, gfn, asce);
+       return cspg_crste(crstep, old, new);
+}
+
+static void dat_set_storage_key_from_pgste(union pte pte, union pgste pgste)
+{
+       union skey nkey = { .acc = pgste.acc, .fp = pgste.fp };
+
+       page_set_storage_key(pte_origin(pte), nkey.skey, 0);
+}
+
+static void dat_move_storage_key(union pte old, union pte new)
+{
+       page_set_storage_key(pte_origin(new), page_get_storage_key(pte_origin(old)), 1);
+}
+
+static union pgste dat_save_storage_key_into_pgste(union pte pte, union pgste pgste)
+{
+       union skey skey;
+
+       skey.skey = page_get_storage_key(pte_origin(pte));
+
+       pgste.acc = skey.acc;
+       pgste.fp = skey.fp;
+       pgste.gr |= skey.r;
+       pgste.gc |= skey.c;
+
+       return pgste;
+}
+
+union pgste __dat_ptep_xchg(union pte *ptep, union pgste pgste, union pte new, gfn_t gfn,
+                           union asce asce, bool uses_skeys)
+{
+       union pte old = READ_ONCE(*ptep);
+
+       /* Updating only the software bits while holding the pgste lock. */
+       if (!((ptep->val ^ new.val) & ~_PAGE_SW_BITS)) {
+               WRITE_ONCE(ptep->swbyte, new.swbyte);
+               return pgste;
+       }
+
+       if (!old.h.i) {
+               unsigned long opts = IPTE_GUEST_ASCE | (pgste.nodat ? IPTE_NODAT : 0);
+
+               if (machine_has_tlb_guest())
+                       __ptep_ipte(gfn_to_gpa(gfn), (void *)ptep, opts, asce.val, IPTE_GLOBAL);
+               else
+                       __ptep_ipte(gfn_to_gpa(gfn), (void *)ptep, 0, 0, IPTE_GLOBAL);
+       }
+
+       if (uses_skeys) {
+               if (old.h.i && !new.h.i)
+                       /* Invalid to valid: restore storage keys from PGSTE. */
+                       dat_set_storage_key_from_pgste(new, pgste);
+               else if (!old.h.i && new.h.i)
+                       /* Valid to invalid: save storage keys to PGSTE. */
+                       pgste = dat_save_storage_key_into_pgste(old, pgste);
+               else if (!old.h.i && !new.h.i)
+                       /* Valid to valid: move storage keys. */
+                       if (old.h.pfra != new.h.pfra)
+                               dat_move_storage_key(old, new);
+               /* Invalid to invalid: nothing to do. */
+       }
+
+       WRITE_ONCE(*ptep, new);
+       return pgste;
+}

diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h
index a053f0d49bae423c4d2763c69f2610f7433dfa8a..ee070d18bd3668c0ddd14de06ab00b2ba9c229cb 100644 (file)
--- a/arch/s390/kvm/dat.h
+++ b/arch/s390/kvm/dat.h
@@ -430,6 +430,12 @@ struct kvm_s390_mmu_cache {
        short int n_rmaps;
 };
 
+union pgste __must_check __dat_ptep_xchg(union pte *ptep, union pgste pgste, union pte new,
+                                        gfn_t gfn, union asce asce, bool uses_skeys);
+bool dat_crstep_xchg_atomic(union crste *crstep, union crste old, union crste new, gfn_t gfn,
+                           union asce asce);
+void dat_crstep_xchg(union crste *crstep, union crste new, gfn_t gfn, union asce asce);
+
 void dat_free_level(struct crst_table *table, bool owns_ptes);
 struct crst_table *dat_alloc_crst_sleepable(unsigned long init);
 
@@ -757,6 +763,21 @@ static inline void pgste_set_unlock(union pte *ptep, union pgste pgste)
        WRITE_ONCE(*pgste_of(ptep), pgste);
 }
 
+static inline void dat_ptep_xchg(union pte *ptep, union pte new, gfn_t gfn, union asce asce,
+                                bool has_skeys)
+{
+       union pgste pgste;
+
+       pgste = pgste_get_lock(ptep);
+       pgste = __dat_ptep_xchg(ptep, pgste, new, gfn, asce, has_skeys);
+       pgste_set_unlock(ptep, pgste);
+}
+
+static inline void dat_ptep_clear(union pte *ptep, gfn_t gfn, union asce asce, bool has_skeys)
+{
+       dat_ptep_xchg(ptep, _PTE_EMPTY, gfn, asce, has_skeys);
+}
+
 static inline void dat_free_pt(struct page_table *pt)
 {
        free_page((unsigned long)pt);
@@ -794,4 +815,23 @@ static inline struct kvm_s390_mmu_cache *kvm_s390_new_mmu_cache(void)
        return NULL;
 }
 
+static inline bool dat_pmdp_xchg_atomic(union pmd *pmdp, union pmd old, union pmd new,
+                                       gfn_t gfn, union asce asce)
+{
+       return dat_crstep_xchg_atomic(_CRSTEP(pmdp), _CRSTE(old), _CRSTE(new), gfn, asce);
+}
+
+static inline bool dat_pudp_xchg_atomic(union pud *pudp, union pud old, union pud new,
+                                       gfn_t gfn, union asce asce)
+{
+       return dat_crstep_xchg_atomic(_CRSTEP(pudp), _CRSTE(old), _CRSTE(new), gfn, asce);
+}
+
+static inline void dat_crstep_clear(union crste *crstep, gfn_t gfn, union asce asce)
+{
+       union crste newcrste = _CRSTE_EMPTY(crstep->h.tt);
+
+       dat_crstep_xchg(crstep, newcrste, gfn, asce);
+}
+
 #endif /* __KVM_S390_DAT_H */