powerpc/mm: Add pte_xchg() helper

We have five locations in 64-bit hash MMU code that do a cmpxchg() of a
PTE. Currently doing it inline OK, but in a future patch we will be
converting the PTEs to __be64 in some configs. In that case we will need
casts at every cmpxchg() site in order to keep sparse happy.

So move the logic into a helper, this is a reasonably nice cleanup on
its own.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 1 insertions, 4 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 7529aab068f5..42da513fec2d 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -319,11 +319,8 @@ static inline pte_t kvmppc_read_update_linux_pte(pte_t *ptep, int writing)
                 if (writing && pte_write(old_pte))
                         new_pte = pte_mkdirty(new_pte);
 
-                if (pte_val(old_pte) == __cmpxchg_u64((unsigned long *)ptep,
-                                                      pte_val(old_pte),
-                                                      pte_val(new_pte))) {
+                if (pte_xchg(ptep, old_pte, new_pte))
                         break;
-                }
         }
         return new_pte;
 }