[PATCH v2 02/20] KVM: s390: vsie: Move SCAO validation into a function

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

Improve readability as well as allow re-use in coming patches.

In particular add the logic to be able to check the validity of BSCA and
ESCA origin addresses.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
---
 arch/s390/kvm/vsie.c | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 010327a6ebee..6aa44362033c 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));
 
+static inline bool sie_uses_esca(struct kvm_s390_sie_block *scb)
+{
+	return (scb->ecb2 & ECB2_ESCA);
+}
+
 static unsigned long read_scao(struct kvm *kvm, struct kvm_s390_sie_block *scb)
 {
 	unsigned long vsie_sca = READ_ONCE(scb->scaol) & ~0xfUL;
@@ -97,6 +102,25 @@ static int set_validity_icpt(struct kvm_s390_sie_block *scb,
 	return 1;
 }
 
+/* The sca header must not cross pages etc. */
+static int validate_scao(struct kvm_vcpu *vcpu, struct kvm_s390_sie_block *scb, gpa_t gpa)
+{
+	int offset;
+
+	if (gpa < 2 * PAGE_SIZE)
+		return set_validity_icpt(scb, 0x0038U);
+	if ((gpa & ~0x1fffUL) == kvm_s390_get_prefix(vcpu))
+		return set_validity_icpt(scb, 0x0011U);
+
+	if (sie_uses_esca(scb))
+		offset = offsetof(struct esca_block, cpu[0]) - 1;
+	else
+		offset = offsetof(struct bsca_block, cpu[0]) - 1;
+	if ((gpa & PAGE_MASK) != ((gpa + offset) & PAGE_MASK))
+		return set_validity_icpt(scb, 0x003bU);
+	return 0;
+}
+
 /* mark the prefix as unmapped, this will block the VSIE */
 static void prefix_unmapped(struct vsie_page *vsie_page)
 {
@@ -787,20 +811,14 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 
 	gpa = read_scao(vcpu->kvm, scb_o);
 	if (gpa) {
-		if (gpa < 2 * PAGE_SIZE)
-			rc = set_validity_icpt(scb_s, 0x0038U);
-		else if ((gpa & ~0x1fffUL) == kvm_s390_get_prefix(vcpu))
-			rc = set_validity_icpt(scb_s, 0x0011U);
-		else if ((gpa & PAGE_MASK) !=
-			 ((gpa + offsetof(struct bsca_block, cpu[0]) - 1) & PAGE_MASK))
-			rc = set_validity_icpt(scb_s, 0x003bU);
-		if (!rc) {
-			rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
-			if (rc)
-				rc = set_validity_icpt(scb_s, 0x0034U);
-		}
+		rc = validate_scao(vcpu, scb_s, gpa);
 		if (rc)
 			goto unpin;
+		rc = pin_guest_page(vcpu->kvm, gpa, &hpa);
+		if (rc) {
+			rc = set_validity_icpt(scb_s, 0x0034U);
+			goto unpin;
+		}
 		vsie_page->sca_gpa = gpa;
 		write_scao(scb_s, hpa);
 	}

-- 
2.55.0