[PATCH v4 17/27] KVM: s390: Refactor prefix handling into a separate file

[Steffen Eiden <seiden@linux.ibm.com>]

Split prefix page tracking into prefix.c/h with conditional compilation
via prefix-stubs.c for KVM for non-s390 guests. Enables gmap reuse by
other KVM implementations that don't use prefix pages. The prefix
tracking is conditional on the Makefile variable KVM_MANAGES_S390_GUEST.

No functional changes.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
 arch/s390/kvm/gmap/Makefile       |  4 +-
 arch/s390/kvm/gmap/dat.c          | 48 -------------------
 arch/s390/kvm/gmap/gmap.c         | 23 ---------
 arch/s390/kvm/gmap/gmap.h         | 11 +----
 arch/s390/kvm/gmap/prefix-stubs.c | 21 ++++++++
 arch/s390/kvm/gmap/prefix.c       | 80 +++++++++++++++++++++++++++++++
 arch/s390/kvm/gmap/prefix.h       | 68 ++++++++++++++++++++++++++
 7 files changed, 173 insertions(+), 82 deletions(-)
 create mode 100644 arch/s390/kvm/gmap/prefix-stubs.c
 create mode 100644 arch/s390/kvm/gmap/prefix.c
 create mode 100644 arch/s390/kvm/gmap/prefix.h

diff --git a/arch/s390/kvm/gmap/Makefile b/arch/s390/kvm/gmap/Makefile
index a49c7e36b71c..4ca7635d1d0e 100644
--- a/arch/s390/kvm/gmap/Makefile
+++ b/arch/s390/kvm/gmap/Makefile
@@ -4,7 +4,9 @@ GMAP ?= ../gmap
 
 # Enable s390-specific guest management features (storage keys and CMMA)
 KVM_MANAGES_S390_GUEST ?= y
+USE_PREFIX_STUB := $(if $(filter y,$(KVM_MANAGES_S390_GUEST)),n,y)
 
 kvm-y += $(GMAP)/dat.o $(GMAP)/gmap.o $(GMAP)/faultin.o $(GMAP)/mmu.o
 
-kvm-$(KVM_MANAGES_S390_GUEST) += $(GMAP)/sk.o $(GMAP)/cmma.o
+kvm-$(KVM_MANAGES_S390_GUEST) += $(GMAP)/sk.o $(GMAP)/cmma.o $(GMAP)/prefix.o
+kvm-$(USE_PREFIX_STUB) += $(GMAP)/prefix-stubs.o
diff --git a/arch/s390/kvm/gmap/dat.c b/arch/s390/kvm/gmap/dat.c
index 6114ff442837..4a9847139534 100644
--- a/arch/s390/kvm/gmap/dat.c
+++ b/arch/s390/kvm/gmap/dat.c
@@ -777,51 +777,3 @@ bool dat_test_age_gfn(union asce asce, gfn_t start, gfn_t end)
 {
 	return _dat_walk_gfn_range(start, end, asce, &test_age_ops, 0, NULL) > 0;
 }
-
-static long dat_set_pn_crste(union crste *crstep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
-{
-	union crste newcrste, oldcrste;
-	int *n = walk->priv;
-
-	do {
-		oldcrste = READ_ONCE(*crstep);
-		if (!oldcrste.h.fc || oldcrste.h.i || oldcrste.h.p)
-			return 0;
-		if (oldcrste.s.fc1.prefix_notif)
-			break;
-		newcrste = oldcrste;
-		newcrste.s.fc1.prefix_notif = 1;
-	} while (!dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, walk->asce));
-	*n = 2;
-	return 0;
-}
-
-static long dat_set_pn_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
-{
-	int *n = walk->priv;
-	union pgste pgste;
-
-	pgste = pgste_get_lock(ptep);
-	if (!ptep->h.i && !ptep->h.p) {
-		pgste.prefix_notif = 1;
-		*n += 1;
-	}
-	pgste_set_unlock(ptep, pgste);
-	return 0;
-}
-
-int dat_set_prefix_notif_bit(union asce asce, gfn_t gfn)
-{
-	static const struct dat_walk_ops ops = {
-		.pte_entry = dat_set_pn_pte,
-		.pmd_entry = dat_set_pn_crste,
-		.pud_entry = dat_set_pn_crste,
-	};
-
-	int n = 0;
-
-	_dat_walk_gfn_range(gfn, gfn + 2, asce, &ops, DAT_WALK_IGN_HOLES, &n);
-	if (n != 2)
-		return -EAGAIN;
-	return 0;
-}
diff --git a/arch/s390/kvm/gmap/gmap.c b/arch/s390/kvm/gmap/gmap.c
index 4ade7794e990..3dcd1d4c6a29 100644
--- a/arch/s390/kvm/gmap/gmap.c
+++ b/arch/s390/kvm/gmap/gmap.c
@@ -254,29 +254,6 @@ int s390_replace_asce(struct gmap *gmap)
 	return 0;
 }
 
-bool _gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end, bool hint)
-{
-	struct kvm *kvm = gmap->kvm;
-	struct kvm_vcpu *vcpu;
-	gfn_t prefix_gfn;
-	unsigned long i;
-
-	if (is_shadow(gmap))
-		return false;
-	kvm_for_each_vcpu(i, vcpu, kvm) {
-		/* Match against both prefix pages */
-		prefix_gfn = gpa_to_gfn(kvm_s390_get_prefix(vcpu));
-		if (prefix_gfn < end && gfn <= prefix_gfn + 1) {
-			if (hint && kvm_s390_is_in_sie(vcpu))
-				return false;
-			VCPU_EVENT(vcpu, 2, "gmap notifier for %llx-%llx",
-				   gfn_to_gpa(gfn), gfn_to_gpa(end));
-			kvm_s390_sync_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
-		}
-	}
-	return true;
-}
-
 struct clear_young_pte_priv {
 	struct gmap *gmap;
 	bool young;
diff --git a/arch/s390/kvm/gmap/gmap.h b/arch/s390/kvm/gmap/gmap.h
index aa65fe724fdb..0500c8c6c9ca 100644
--- a/arch/s390/kvm/gmap/gmap.h
+++ b/arch/s390/kvm/gmap/gmap.h
@@ -13,6 +13,7 @@
 #include <linux/kvm_host.h>
 
 #include "dat.h"
+#include "prefix.h"
 
 /**
  * enum gmap_flags - Flags of a gmap.
@@ -158,16 +159,6 @@ static inline void gmap_handle_vsie_unshadow_event(struct gmap *parent, gfn_t gf
 		_gmap_handle_vsie_unshadow_event(parent, gfn);
 }
 
-static inline bool gmap_mkold_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end)
-{
-	return _gmap_unmap_prefix(gmap, gfn, end, true);
-}
-
-static inline bool gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end)
-{
-	return _gmap_unmap_prefix(gmap, gfn, end, false);
-}
-
 /**
  * pte_needs_unshadow() -- Check if the pte operations triggers unshadowing.
  * @oldpte: the previous value for the guest pte.
diff --git a/arch/s390/kvm/gmap/prefix-stubs.c b/arch/s390/kvm/gmap/prefix-stubs.c
new file mode 100644
index 000000000000..d1d6286f454a
--- /dev/null
+++ b/arch/s390/kvm/gmap/prefix-stubs.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * These stubs are used when building gmap for non-s390 guests
+ * that don't need prefix page tracking.
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/kvm_types.h>
+
+#include "dat.h"
+#include "prefix.h"
+
+bool _gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end, bool hint)
+{
+	return true;
+}
+
+int dat_set_prefix_notif_bit(union asce asce, gfn_t gfn)
+{
+	return 0;
+}
diff --git a/arch/s390/kvm/gmap/prefix.c b/arch/s390/kvm/gmap/prefix.c
new file mode 100644
index 000000000000..44caffed2da1
--- /dev/null
+++ b/arch/s390/kvm/gmap/prefix.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/kvm_host.h>
+#include <linux/kvm_types.h>
+
+#include "gmap.h"
+#include "dat.h"
+#include "prefix.h"
+#include "../s390/s390.h"
+
+bool _gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end, bool hint)
+{
+	struct kvm *kvm = gmap->kvm;
+	struct kvm_vcpu *vcpu;
+	gfn_t prefix_gfn;
+	unsigned long i;
+
+	if (is_shadow(gmap))
+		return false;
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		/* Match against both prefix pages */
+		prefix_gfn = gpa_to_gfn(kvm_s390_get_prefix(vcpu));
+		if (prefix_gfn < end && gfn <= prefix_gfn + 1) {
+			if (hint && kvm_s390_is_in_sie(vcpu))
+				return false;
+			VCPU_EVENT(vcpu, 2, "gmap notifier for %llx-%llx",
+				   gfn_to_gpa(gfn), gfn_to_gpa(end));
+			kvm_s390_sync_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
+		}
+	}
+	return true;
+}
+
+static long dat_set_pn_crste(union crste *crstep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
+{
+	union crste newcrste, oldcrste;
+	int *n = walk->priv;
+
+	do {
+		oldcrste = READ_ONCE(*crstep);
+		if (!oldcrste.h.fc || oldcrste.h.i || oldcrste.h.p)
+			return 0;
+		if (oldcrste.s.fc1.prefix_notif)
+			break;
+		newcrste = oldcrste;
+		newcrste.s.fc1.prefix_notif = 1;
+	} while (!dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, walk->asce));
+	*n = 2;
+	return 0;
+}
+
+static long dat_set_pn_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
+{
+	int *n = walk->priv;
+	union pgste pgste;
+
+	pgste = pgste_get_lock(ptep);
+	if (!ptep->h.i && !ptep->h.p) {
+		pgste.prefix_notif = 1;
+		*n += 1;
+	}
+	pgste_set_unlock(ptep, pgste);
+	return 0;
+}
+
+int dat_set_prefix_notif_bit(union asce asce, gfn_t gfn)
+{
+	static const struct dat_walk_ops ops = {
+		.pte_entry = dat_set_pn_pte,
+		.pmd_entry = dat_set_pn_crste,
+		.pud_entry = dat_set_pn_crste,
+	};
+
+	int n = 0;
+
+	_dat_walk_gfn_range(gfn, gfn + 2, asce, &ops, DAT_WALK_IGN_HOLES, &n);
+	if (n != 2)
+		return -EAGAIN;
+	return 0;
+}
diff --git a/arch/s390/kvm/gmap/prefix.h b/arch/s390/kvm/gmap/prefix.h
new file mode 100644
index 000000000000..f1f3ace24f03
--- /dev/null
+++ b/arch/s390/kvm/gmap/prefix.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef ARCH_KVM_GMAP_PREFIX_H
+#define ARCH_KVM_GMAP_PREFIX_H
+
+#include <linux/types.h>
+#include <linux/kvm_types.h>
+
+struct gmap;
+union asce;
+
+/**
+ * _gmap_unmap_prefix() - Notify vCPUs if prefix pages are affected
+ * @gmap: The gmap
+ * @gfn: Start of the range
+ * @end: End of the range (exclusive)
+ * @hint: If true, skip notification if vCPU is in SIE
+ *
+ * Check if any vCPU's prefix pages fall within the given range and
+ * request prefix refresh if needed.
+ *
+ * Return: false if notification was skipped due to hint, true otherwise
+ */
+bool _gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end, bool hint);
+
+/**
+ * dat_set_prefix_notif_bit() - Set prefix notification bits
+ * @asce: The address space control element
+ * @gfn: Guest frame number of the prefix area
+ *
+ * Set the prefix notification bit in the page table entries for the
+ * two prefix pages starting at @gfn.
+ *
+ * Return: 0 on success, -EAGAIN if not all bits could be set
+ */
+int dat_set_prefix_notif_bit(union asce asce, gfn_t gfn);
+
+/**
+ * gmap_mkold_prefix() - Mark prefix pages as old
+ * @gmap: The gmap
+ * @gfn: Start of the range
+ * @end: End of the range (exclusive)
+ *
+ * Inline wrapper that calls _gmap_unmap_prefix with hint=true.
+ *
+ * Return: Result from _gmap_unmap_prefix
+ */
+static inline bool gmap_mkold_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end)
+{
+	return _gmap_unmap_prefix(gmap, gfn, end, true);
+}
+
+/**
+ * gmap_unmap_prefix() - Unconditionally notify about prefix pages
+ * @gmap: The gmap
+ * @gfn: Start of the range
+ * @end: End of the range (exclusive)
+ *
+ * Inline wrapper that calls _gmap_unmap_prefix with hint=false.
+ *
+ * Return: Result from _gmap_unmap_prefix
+ */
+static inline bool gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end)
+{
+	return _gmap_unmap_prefix(gmap, gfn, end, false);
+}
+
+#endif /* ARCH_KVM_GMAP_PREFIX_H */
-- 
2.53.0