[PATCH v2 12/20] KVM: s390: vsie: Add helper to pin and unpin multiple guest pages

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

To handle vSIE configurations with an ssca 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.

Since the new methods use the existing {,un}pin_guest_page() helpers,
they are moved up unchanged in the file to avoid having to resort to
forward declarations later on.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/vsie.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 4f4d35e0c8c1..0bbb65300a85 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -71,6 +71,11 @@ static_assert(sizeof(struct vsie_page) == PAGE_SIZE);
 static_assert(offsetof(struct vsie_page, mcck_info) == offsetof(struct sie_page, mcck_info));
 static_assert(IS_ALIGNED(offsetof(struct vsie_page, crycb), 8));
 
+struct kvm_address_pair {
+	gpa_t gpa;
+	hpa_t hpa;
+};
+
 static inline bool sie_uses_esca(struct kvm_s390_sie_block *scb)
 {
 	return (scb->ecb2 & ECB2_ESCA);
@@ -249,6 +254,46 @@ static void unpin_guest_page(struct kvm *kvm, gpa_t gpa, hpa_t hpa)
 	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
+ *
+ * Returns number of pages pinned or -EFAULT.
+ */
+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;
+
+	gpa = gpa & PAGE_MASK;
+
+	/* 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)
 {

-- 
2.55.0