powerpc/64s: Default l1d_size to 64K in RFI fallback flush

Madhavan Srinivasan · mpe · commit 9dfbf78e4114 · 2018-04-17T19:29:04.000+10:00
If there is no d-cache-size property in the device tree, l1d_size could be zero. We don't actually expect that to happen, it's only been seen on mambo (simulator) in some configurations. A zero-size l1d_size leads to the loop in the asm wrapping around to 2^64-1, and then walking off the end of the fallback area and eventually causing a page fault which is fatal. Just default to 64K which is correct on some CPUs, and sane enough to not cause a crash on others. Fixes: aa8a5e0 ('powerpc/64s: Add support for RFI flush of L1-D cache') Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> [mpe: Rewrite comment and change log] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
@@ -890,6 +890,17 @@ static void __ref init_fallback_flush(void)
 		return;
 
 	l1d_size = ppc64_caches.l1d.size;
+
+	/*
+	 * If there is no d-cache-size property in the device tree, l1d_size
+	 * could be zero. That leads to the loop in the asm wrapping around to
+	 * 2^64-1, and then walking off the end of the fallback area and
+	 * eventually causing a page fault which is fatal. Just default to
+	 * something vaguely sane.
+	 */
+	if (!l1d_size)
+		l1d_size = (64 * 1024);
+
 	limit = min(ppc64_bolted_size(), ppc64_rma_size);
 
 	/*
