xen-hvm: increase maxmem before calling xc_domain_populate_physmap

Increase maxmem before calling xc_domain_populate_physmap_exact to
avoid the risk of running out of guest memory. This way we can also
avoid complex memory calculations in libxl at domain construction
time.

This patch fixes an abort() when assigning more than 4 NICs to a VM.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Don Slutz <dslutz@verizon.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/xen-hvm.c b/xen-hvm.c
index 7548794..e2e575b 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -90,6 +90,12 @@ static inline ioreq_t *xen_vcpu_ioreq(shared_iopage_t *shared_page, int vcpu)
 #endif
 
 #define BUFFER_IO_MAX_DELAY  100
+/* Leave some slack so that hvmloader does not complain about lack of
+ * memory at boot time ("Could not allocate order=0 extent").
+ * Once hvmloader is modified to cope with that situation without
+ * printing warning messages, QEMU_SPARE_PAGES can be removed.
+ */
+#define QEMU_SPARE_PAGES 16
 
 typedef struct XenPhysmap {
     hwaddr start_addr;
@@ -244,6 +250,8 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr)
     unsigned long nr_pfn;
     xen_pfn_t *pfn_list;
     int i;
+    xc_domaininfo_t info;
+    unsigned long free_pages;
 
     if (runstate_check(RUN_STATE_INMIGRATE)) {
         /* RAM already populated in Xen */
@@ -266,6 +274,22 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr)
         pfn_list[i] = (ram_addr >> TARGET_PAGE_BITS) + i;
     }
 
+    if ((xc_domain_getinfolist(xen_xc, xen_domid, 1, &info) != 1) ||
+        (info.domain != xen_domid)) {
+        hw_error("xc_domain_getinfolist failed");
+    }
+    free_pages = info.max_pages - info.tot_pages;
+    if (free_pages > QEMU_SPARE_PAGES) {
+        free_pages -= QEMU_SPARE_PAGES;
+    } else {
+        free_pages = 0;
+    }
+    if ((free_pages < nr_pfn) &&
+        (xc_domain_setmaxmem(xen_xc, xen_domid,
+                             ((info.max_pages + nr_pfn - free_pages)
+                              << (XC_PAGE_SHIFT - 10))) < 0)) {
+        hw_error("xc_domain_setmaxmem failed");
+    }
     if (xc_domain_populate_physmap_exact(xen_xc, xen_domid, nr_pfn, 0, 0, pfn_list)) {
         hw_error("xen: failed to populate ram at " RAM_ADDR_FMT, ram_addr);
     }