KVM: Add function comments for __kvm_read/write_guest_page()

The (gfn, data, offset, len) order of parameters is a little strange
since "offset" applies to "gfn" rather than to "data". Add function
comments to make things perfectly clear.
Signed-off-by: Anish Moorthy <amoorthy@google.com>
Link: https://lore.kernel.org/r/20240215235405.368539-3-amoorthy@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

virt/kvm/kvm_main.c

@@ -3308,6 +3308,7 @@ static int next_segment(unsigned long len, int offset)
 		return len;
 }
 
+/* Copy @len bytes from guest memory at '(@gfn * PAGE_SIZE) + @offset' to @data */
 static int __kvm_read_guest_page(struct kvm_memory_slot *slot, gfn_t gfn,
 				 void *data, int offset, int len)
 {
@@ -3409,6 +3410,7 @@ int kvm_vcpu_read_guest_atomic(struct kvm_vcpu *vcpu, gpa_t gpa,
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_read_guest_atomic);
 
+/* Copy @len bytes from @data into guest memory at '(@gfn * PAGE_SIZE) + @offset' */
 static int __kvm_write_guest_page(struct kvm *kvm,
 				  struct kvm_memory_slot *memslot, gfn_t gfn,
 			          const void *data, int offset, int len)