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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Gabriel Bercarug <bercarug@amazon.com>,
        =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>,
        Juergen Gross <jgross@suse.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 110/197] xen/balloon: fix balloon initialization for PVH Dom0
Date:   Thu, 13 Sep 2018 15:30:59 +0200
Message-Id: <20180913131845.947930771@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Roger Pau Monne <roger.pau@citrix.com>

[ Upstream commit 3596924a233e45aa918c961a902170fc4916461b ]

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@amazon.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/xen/xen-balloon.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/xen/xen-balloon.c
+++ b/drivers/xen/xen-balloon.c
@@ -81,7 +81,7 @@ static void watch_target(struct xenbus_w
 			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;
 	}