linux-kernel - [PATCH v2 1/3] KVM: s390: gaccess: Refactor gpa and length calculation

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Message-Id: <20211028135556.1793063-2-scgl@linux.ibm.com>
Date:   Thu, 28 Oct 2021 15:55:54 +0200
From:   Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Cc:     Janis Schoetterl-Glausch <scgl@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] KVM: s390: gaccess: Refactor gpa and length calculation

Improve readability be renaming the length variable and
not calculating the offset manually.

Signed-off-by: Janis Schoetterl-Glausch <scgl@...ux.ibm.com>
---
 arch/s390/kvm/gaccess.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 6af59c59cc1b..0d11cea92603 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -831,7 +831,8 @@ 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 fragment_len;
 	unsigned long pages_array[2];
 	unsigned long *pages;
 	int need_ipte_lock;
@@ -855,15 +856,15 @@ 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);
+		gpa = pages[idx] + offset_in_page(ga);
+		fragment_len = min(PAGE_SIZE - offset_in_page(gpa), len);
 		if (mode == GACC_STORE)
-			rc = kvm_write_guest(vcpu->kvm, gpa, data, _len);
+			rc = kvm_write_guest(vcpu->kvm, gpa, data, fragment_len);
 		else
-			rc = kvm_read_guest(vcpu->kvm, gpa, data, _len);
-		len -= _len;
-		ga += _len;
-		data += _len;
+			rc = kvm_read_guest(vcpu->kvm, gpa, data, fragment_len);
+		len -= fragment_len;
+		ga += fragment_len;
+		data += fragment_len;
 	}
 	if (need_ipte_lock)
 		ipte_unlock(vcpu);
@@ -875,19 +876,20 @@ 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 int fragment_len;
+	unsigned long gpa;
 	int rc = 0;
 
 	while (len && !rc) {
 		gpa = kvm_s390_real_to_abs(vcpu, gra);
-		_len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
+		fragment_len = min(PAGE_SIZE - offset_in_page(gpa), len);
 		if (mode)
-			rc = write_guest_abs(vcpu, gpa, data, _len);
+			rc = write_guest_abs(vcpu, gpa, data, fragment_len);
 		else
-			rc = read_guest_abs(vcpu, gpa, data, _len);
-		len -= _len;
-		gra += _len;
-		data += _len;
+			rc = read_guest_abs(vcpu, gpa, data, fragment_len);
+		len -= fragment_len;
+		gra += fragment_len;
+		data += fragment_len;
 	}
 	return rc;
 }
-- 
2.25.1