On 8/18/21 9:54 AM, David Hildenbrand wrote:

On 16.08.21 17:07, Janis Schoetterl-Glausch wrote:

quoted

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 <redacted>

[...]

quoted

-	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);

What does "seg" mean? I certainly know when "len" means -- which is also 
what the function eats.

What does "_len" mean especially in contrast to "len"?

"seg" is used in the common kvm guest access functions so it's at least
consistent although I share the sentiment that it's not a great name for
the length we access inside the page.

Originally I suggested "len_in_page" if you have a better name I'd
expect we'll both be happy to discuss it :-)

quoted

+		rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg);
+		len -= seg;
+		gra += seg;
+		data += seg;
  	}
  	return rc;
  }