linux-kernel - [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames

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Date:   Mon, 16 Aug 2021 17:07:16 +0200
From:   Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
To:     kvm@...r.kernel.org, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        imbrenda@...ux.ibm.com, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Cc:     scgl@...ux.ibm.com, david@...hat.com, cohuck@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames

Introduce a helper function for guest frame access.
Rewrite the calculation of the gpa and the length of the segment
to be more readable.

Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
---
 arch/s390/kvm/gaccess.c | 48 +++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 19 deletions(-)

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index b9f85b2dc053..df83de0843de 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -827,11 +827,26 @@ static int guest_page_range(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
 	return 0;
 }
 
+static int access_guest_frame(struct kvm *kvm, enum gacc_mode mode, gpa_t gpa,
+			      void *data, unsigned int len)
+{
+	gfn_t gfn = gpa_to_gfn(gpa);
+	unsigned int offset = offset_in_page(gpa);
+	int rc;
+
+	if (mode == GACC_STORE)
+		rc = kvm_write_guest_page(kvm, gfn, data, offset, len);
+	else
+		rc = kvm_read_guest_page(kvm, gfn, data, offset, len);
+	return rc;
+}
+
 int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
 		 unsigned long len, enum gacc_mode mode)
 {
 	psw_t *psw = &vcpu->arch.sie_block->gpsw;
-	unsigned long _len, nr_pages, gpa, idx;
+	unsigned long nr_pages, gpa, idx;
+	unsigned int seg;
 	unsigned long pages_array[2];
 	unsigned long *pages;
 	int need_ipte_lock;
@@ -855,15 +870,12 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
 		ipte_lock(vcpu);
 	rc = guest_page_range(vcpu, ga, ar, pages, nr_pages, asce, mode);
 	for (idx = 0; idx < nr_pages && !rc; idx++) {
-		gpa = *(pages + idx) + (ga & ~PAGE_MASK);
-		_len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
-		if (mode == GACC_STORE)
-			rc = kvm_write_guest(vcpu->kvm, gpa, data, _len);
-		else
-			rc = kvm_read_guest(vcpu->kvm, gpa, data, _len);
-		len -= _len;
-		ga += _len;
-		data += _len;
+		gpa = pages[idx] + offset_in_page(ga);
+		seg = min(PAGE_SIZE - offset_in_page(gpa), len);
+		rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg);
+		len -= seg;
+		ga += seg;
+		data += seg;
 	}
 	if (need_ipte_lock)
 		ipte_unlock(vcpu);
@@ -875,19 +887,17 @@ int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
 int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
 		      void *data, unsigned long len, enum gacc_mode mode)
 {
-	unsigned long _len, gpa;
+	unsigned long gpa;
+	unsigned int seg;
 	int rc = 0;
 
 	while (len && !rc) {
 		gpa = kvm_s390_real_to_abs(vcpu, gra);
-		_len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
-		if (mode)
-			rc = write_guest_abs(vcpu, gpa, data, _len);
-		else
-			rc = read_guest_abs(vcpu, gpa, data, _len);
-		len -= _len;
-		gra += _len;
-		data += _len;
+		seg = min(PAGE_SIZE - offset_in_page(gpa), len);
+		rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg);
+		len -= seg;
+		gra += seg;
+		data += seg;
 	}
 	return rc;
 }
-- 
2.25.1