hypervisor/xen/tools: Remove the XENMEM_get_oustanding_pages and provide the data via xc_phys_info

During the review of the patches it was noticed that there exists
a race wherein the 'free_memory' value consists of information from
two hypercalls. That is the XEN_SYSCTL_physinfo and XENMEM_get_outstanding_pages.

The free memory the host has available for guest is the difference between
the 'free_pages' (from XEN_SYSCTL_physinfo) and 'outstanding_pages'. As they
are two hypercalls many things can happen in between the execution of them.

This patch resolves this by eliminating the XENMEM_get_outstanding_pages
hypercall and providing the free_pages and outstanding_pages information
via the xc_phys_info structure.

It also removes the XSM hooks and adds locking as needed.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Tim Deegan <tim@xen.org>
Acked-by: Keir Fraser <keir.xen@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index 31f9650ecc..117e095a35 100644
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -264,7 +264,8 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
         pi->max_node_id = MAX_NUMNODES-1;
         pi->max_cpu_id = nr_cpu_ids - 1;
         pi->total_pages = total_pages;
-        pi->free_pages = avail_domheap_pages();
+        /* Protected by lock */
+        get_outstanding_claims(&pi->free_pages, &pi->outstanding_pages);
         pi->scrub_pages = 0;
         pi->cpu_khz = cpu_khz;
         arch_do_physinfo(pi);