KVM: pfncache: stop open-coding offset_in_page()

Some code in pfncache uses offset_in_page() but in other places it is open-
coded. Use offset_in_page() consistently everywhere.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240215152916.1158-7-paul@xen.org
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: Paul Durrant

virt/kvm/pfncache.c

@@ -48,7 +48,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)
 	if (!gpc->active)
 		return false;
 
-	if ((gpc->gpa & ~PAGE_MASK) + len > PAGE_SIZE)
+	if (offset_in_page(gpc->gpa) + len > PAGE_SIZE)
 		return false;
 
 	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))
@@ -192,7 +192,7 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc)
 
 	gpc->valid = true;
 	gpc->pfn = new_pfn;
-	gpc->khva = new_khva + (gpc->gpa & ~PAGE_MASK);
+	gpc->khva = new_khva + offset_in_page(gpc->gpa);
 
 	/*
 	 * Put the reference to the _new_ pfn.  The pfn is now tracked by the
@@ -213,7 +213,7 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
 			     unsigned long len)
 {
 	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
-	unsigned long page_offset = gpa & ~PAGE_MASK;
+	unsigned long page_offset = offset_in_page(gpa);
 	bool unmap_old = false;
 	unsigned long old_uhva;
 	kvm_pfn_t old_pfn;