[PATCH RFC v2 06/11] KVM: s390: Add helper to pin multiple guest pages

[Christoph Schlameuss <schlameuss@linux.ibm.com>]

In the main patch of this set we need to pin and unpin multiple
consecutive guest-2 pages in guest-1. As these might not be consecutive
in guest-1 it is necessary to iterate over all pages and store guest and
host addresses for later use.

As the new methods to use the existing {,un}pin_guest_page() methods
these are moved up unchanged in the file to prevent to have to resort to
forward declarations later on.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/vsie.c | 91 +++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 65 insertions(+), 26 deletions(-)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 3d602bbd1f70b7bd8ddc2c54d43027dc37a6e032..e86fef0fa3919668902c766813991572c2311b09 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -67,6 +67,11 @@ struct vsie_page {
 	__u8 fac[S390_ARCH_FAC_LIST_SIZE_BYTE];	/* 0x0800 */
 };
 
+struct kvm_address_pair {
+	gpa_t gpa;
+	hpa_t hpa;
+};
+
 /**
  * gmap_shadow_valid() - check if a shadow guest address space matches the
  *                       given properties and is still valid
@@ -159,6 +164,66 @@ static void write_scao(struct kvm_s390_sie_block *scb, hpa_t hpa)
 	scb->scaol = (u32)(u64)hpa;
 }
 
+/*
+ * Pin the guest page given by gpa and set hpa to the pinned host address.
+ * Will always be pinned writable.
+ *
+ * Returns: - 0 on success
+ *          - -EINVAL if the gpa is not valid guest storage
+ */
+static int pin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t *hpa)
+{
+	struct page *page;
+
+	page = gfn_to_page(kvm, gpa_to_gfn(gpa));
+	if (!page)
+		return -EINVAL;
+	*hpa = (hpa_t)page_to_phys(page) + (gpa & ~PAGE_MASK);
+	return 0;
+}
+
+/* Unpins a page previously pinned via pin_guest_page, marking it as dirty. */
+static void unpin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t hpa)
+{
+	kvm_release_page_dirty(pfn_to_page(hpa >> PAGE_SHIFT));
+	/* mark the page always as dirty for migration */
+	mark_page_dirty(kvm, gpa_to_gfn(gpa));
+}
+
+/* unpin multiple guest pages pinned with pin_guest_pages() */
+static void unpin_guest_pages(struct kvm *kvm, struct kvm_address_pair *addr, unsigned int nr_pages)
+{
+	int i;
+
+	for (i = 0; i < nr_pages; i++) {
+		unpin_guest_page(kvm, addr[i].gpa, addr[i].hpa);
+		addr[i].gpa = 0;
+		addr[i].hpa = 0;
+	}
+}
+
+/* pin nr_pages consecutive guest pages */
+static int pin_guest_pages(struct kvm *kvm, gpa_t gpa, unsigned int nr_pages,
+			   struct kvm_address_pair *addr)
+{
+	hpa_t hpa;
+	int i, rc;
+
+	/* the guest pages may not be mapped continuously, so pin each page */
+	for (i = 0; i < nr_pages; i++) {
+		rc = pin_guest_page(kvm, gpa + PAGE_SIZE * i, &hpa);
+		if (rc)
+			goto err;
+		addr[i].gpa = gpa + PAGE_SIZE * i;
+		addr[i].hpa = hpa;
+	}
+	return i;
+
+err:
+	unpin_guest_pages(kvm, addr, i);
+	return -EFAULT;
+}
+
 /* copy the updated intervention request bits into the shadow scb */
 static void update_intervention_requests(struct vsie_page *vsie_page)
 {
@@ -718,32 +783,6 @@ static int map_prefix(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	return rc;
 }
 
-/*
- * Pin the guest page given by gpa and set hpa to the pinned host address.
- * Will always be pinned writable.
- *
- * Returns: - 0 on success
- *          - -EINVAL if the gpa is not valid guest storage
- */
-static int pin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t *hpa)
-{
-	struct page *page;
-
-	page = gfn_to_page(kvm, gpa_to_gfn(gpa));
-	if (!page)
-		return -EINVAL;
-	*hpa = (hpa_t)page_to_phys(page) + (gpa & ~PAGE_MASK);
-	return 0;
-}
-
-/* Unpins a page previously pinned via pin_guest_page, marking it as dirty. */
-static void unpin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t hpa)
-{
-	kvm_release_page_dirty(pfn_to_page(hpa >> PAGE_SHIFT));
-	/* mark the page always as dirty for migration */
-	mark_page_dirty(kvm, gpa_to_gfn(gpa));
-}
-
 /* unpin all blocks previously pinned by pin_blocks(), marking them dirty */
 static void unpin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {

-- 
2.51.1