Commit 3aa6c19d2f38be ("xen/balloon: Support xend-based toolstack") tried to fix a regression with running on rather ancient Xen versions. Unfortunately the fix was based on the assumption that xend would just use another Xenstore node, but in reality only some downstream versions of xend are doing that. The upstream xend does not write that Xenstore node at all, so the problem must be fixed in another way.

The easiest way to achieve that is to fall back to the behavior before commit 96edd61dcf4436 ("xen/balloon: don't online new memory initially") in case the static memory maximum can't be read.

This is achieved by setting static_max to the current number of memory pages known by the system resulting in target_diff becoming zero.

Fixes: 3aa6c19d2f38be ("xen/balloon: Support xend-based toolstack") Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: stable@vger.kernel.org # 4.13 --- V2: better commit message --- 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 6d12fc368210..a8d24433c8e9 100644 --- a/drivers/xen/xen-balloon.c +++ b/drivers/xen/xen-balloon.c @@ -94,7 +94,7 @@ static void watch_target(struct xenbus_watch *watch, "%llu", &static_max) == 1)) static_max >>= PAGE_SHIFT - 10; else - static_max = new_target; + static_max = balloon_stats.current_pages;

target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0 : static_max - balloon_stats.target_pages;