powerpc/powernv/memtrace: Fix dcache flushing

Trace memory is cleared and the corresponding dcache lines
are flushed after allocation. However, this should not be
done using the PFN. This adds the missing conversion to
virtual address.

Fixes: 2ac02e5e ("powerpc/mm: Remove dcache flush from memory remove.")
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210501160254.1179831-1-sandipan@linux.ibm.com

arch/powerpc/platforms/powernv/memtrace.c

@@ -104,8 +104,8 @@ static void memtrace_clear_range(unsigned long start_pfn,
 	 * Before we go ahead and use this range as cache inhibited range
 	 * flush the cache.
 	 */
-	flush_dcache_range_chunked(PFN_PHYS(start_pfn),
-				   PFN_PHYS(start_pfn + nr_pages),
+	flush_dcache_range_chunked((unsigned long)pfn_to_kaddr(start_pfn),
+				   (unsigned long)pfn_to_kaddr(start_pfn + nr_pages),
 				   FLUSH_CHUNK_SIZE);
 }