diff --git a/src/vendorcode/amd/opensil/genoa_poc/memmap.c b/src/vendorcode/amd/opensil/genoa_poc/memmap.c
index 39b27ec293..31e6f0406c 100644
--- a/src/vendorcode/amd/opensil/genoa_poc/memmap.c
+++ b/src/vendorcode/amd/opensil/genoa_poc/memmap.c
@@ -110,7 +110,7 @@ void add_opensil_memmap(struct device *dev, unsigned long *idx)
 		    mem_usable);
 
 	// Account for UMA and TSEG
-	const uint32_t top_mem = ALIGN_DOWN(rdmsr(TOP_MEM).lo, 1 * MiB);
+	const uint32_t top_mem = ALIGN_DOWN(get_top_of_mem_below_4gb(), 1 * MiB);
 	if (mem_usable != top_mem)
 		reserved_ram_from_to(dev, (*idx)++, mem_usable, top_mem);