[Qemu-devel] [PATCH for 2.3 v2 1/1] xen-hvm: increase maxmem before calling xc_domain_populate_physmap

[Don Slutz <dslutz@verizon.com>]

From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

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>
---
v2: Changes by Don Slutz
  Switch from xc_domain_getinfo to xc_domain_getinfolist
  Fix error check for xc_domain_getinfolist
  Limit increase of maxmem to only do when needed:
    Add QEMU_SPARE_PAGES (How many pages to leave free)
    Add free_pages calculation

 xen-hvm.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/xen-hvm.c b/xen-hvm.c
index 7548794..d30e77e 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -90,6 +90,7 @@ static inline ioreq_t *xen_vcpu_ioreq(shared_iopage_t *shared_page, int vcpu)
 #endif
 
 #define BUFFER_IO_MAX_DELAY  100
+#define QEMU_SPARE_PAGES 16
 
 typedef struct XenPhysmap {
     hwaddr start_addr;
@@ -244,6 +245,8 @@ 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 +269,22 @@ 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);
     }
-- 
1.8.4