From 9dfbf78e4114fcaf4ef61c49885c3ab5bad40d0b Mon Sep 17 00:00:00 2001
From: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Date: Thu, 18 Jan 2018 00:33:36 +0530
Subject: [PATCH] powerpc/64s: Default l1d_size to 64K in RFI fallback flush

References: bsc#1068032, git-fixes
Patch-mainline: v4.17-rc2
Git-commit: 9dfbf78e4114fcaf4ef61c49885c3ab5bad40d0b

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: aa8a5e0062ac9 ('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>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kernel/setup_64.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 44c30dd38067..b78f142a4148 100644
--- 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);
 
 	/*
-- 
2.13.7