From 5081efd112560d3febb328e627176235b250d59d Mon Sep 17 00:00:00 2001
From: Nadav Amit <namit@vmware.com>
Date: Tue, 19 Jun 2018 16:00:25 -0700
Subject: [PATCH] vmw_balloon: do not use 2MB without batching
Git-commit: 5081efd112560d3febb328e627176235b250d59d
Patch-mainline: v4.19-rc1
References: bsc#1051510

If the hypervisor sets 2MB batching is on, while batching is cleared,
the balloon code breaks. In this case the legacy mechanism is used with
2MB page. The VM would report a 2MB page is ballooned, and the
hypervisor would only take the first 4KB.

While the hypervisor should not report such settings, make the code more
robust by not enabling 2MB support without batching.

Fixes: 365bd7ef7ec8e ("VMware balloon: Support 2m page ballooning.")
Cc: stable@vger.kernel.org
Reviewed-by: Xavier Deguillard <xdeguillard@vmware.com>
Signed-off-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/misc/vmw_balloon.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
index 28e77ab1e136..60ab83d3d0ef 100644
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -341,7 +341,13 @@ static bool vmballoon_send_start(struct vmballoon *b, unsigned long req_caps)
 		success = false;
 	}
 
-	if (b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS)
+	/*
+	 * 2MB pages are only supported with batching. If batching is for some
+	 * reason disabled, do not use 2MB pages, since otherwise the legacy
+	 * mechanism is used with 2MB pages, causing a failure.
+	 */
+	if ((b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS) &&
+	    (b->capabilities & VMW_BALLOON_BATCHED_CMDS))
 		b->supported_page_sizes = 2;
 	else
 		b->supported_page_sizes = 1;
-- 
2.18.0