From d6b5b105305dcc2c200ab82b942489902ef7dc7a Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Sun, 24 Oct 2010 13:13:04 +0100 Subject: [PATCH] Allow max_pages to be set to less than tot_pages The memory allocation code sometimes needs to enforce that a guest that's been told to balloon down isn't going to expand further (because it's still executing a previous balloon-up operation). That means being able to set the desired max_pages even before the balloon driver has brought tot_pages down to the right level. Signed-off-by: Tim Deegan Acked-by: Ian Jackson --- xen/common/domctl.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/xen/common/domctl.c b/xen/common/domctl.c index 7bc976eb79..f45c62e93c 100644 --- a/xen/common/domctl.c +++ b/xen/common/domctl.c @@ -770,11 +770,13 @@ long do_domctl(XEN_GUEST_HANDLE(xen_domctl_t) u_domctl) new_max = op->u.max_mem.max_memkb >> (PAGE_SHIFT-10); spin_lock(&d->page_alloc_lock); - if ( new_max >= d->tot_pages ) - { - d->max_pages = new_max; - ret = 0; - } + /* + * NB. We removed a check that new_max >= current tot_pages; this means + * that the domain will now be allowed to "ratchet" down to new_max. In + * the meantime, while tot > max, all new allocations are disallowed. + */ + d->max_pages = new_max; + ret = 0; spin_unlock(&d->page_alloc_lock); max_mem_out: -- 2.30.2