linux-kernel - [PATCH] xen/balloon: fix balloon initialization for PVH Dom0

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Date:   Wed, 8 Aug 2018 13:46:41 +0200
From:   Roger Pau Monne <roger.pau@...rix.com>
To:     <linux-kernel@...r.kernel.org>
CC:     Roger Pau Monne <roger.pau@...rix.com>,
        Gabriel Ercarug <bercarug@...zon.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        <xen-devel@...ts.xenproject.org>
Subject: [PATCH] xen/balloon: fix balloon initialization for PVH Dom0

The current balloon code tries to calculate a delta factor for the
balloon target when running in HVM mode in order to account for memory
used by the firmware.

This workaround for memory accounting doesn't work properly on a PVH
Dom0, that has a static-max value different from the target value even
at startup. Note that this is not a problem for DomUs because guests are
started with a static-max value that matches the amount of RAM in the
memory map.

Fix this by forcefully setting target_diff for Dom0, regardless of
it's mode.

Reported-by: Gabriel Bercarug <bercarug@...zon.com>
Signed-off-by: Roger Pau Monné <roger.pau@...rix.com>
---
Cc: Gabriel Ercarug <bercarug@...zon.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: xen-devel@...ts.xenproject.org
---
 drivers/xen/xen-balloon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
index b437fccd4e62..294f35ce9e46 100644
--- a/drivers/xen/xen-balloon.c
+++ b/drivers/xen/xen-balloon.c
@@ -81,7 +81,7 @@ static void watch_target(struct xenbus_watch *watch,
 			static_max = new_target;
 		else
 			static_max >>= PAGE_SHIFT - 10;
-		target_diff = xen_pv_domain() ? 0
+		target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
 				: static_max - balloon_stats.target_pages;
 	}
 
-- 
2.18.0