[Xen-devel] [PATCH] linux/balloon: fix accounting for HVM-with-PoD case

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

With PoD, ballooning down a guest to the target set through xenstore
based on its totalram_pages value isn't sufficient, since that value
doesn't include all the pages assigned to the guest. Since the delta
is static, determine it once at load time.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- sle11-2010-01-12.orig/drivers/xen/balloon/balloon.c 2009-08-31 
11:48:33.000000000 +0200
+++ sle11-2010-01-12/drivers/xen/balloon/balloon.c      2010-02-01 
13:35:47.000000000 +0100
@@ -90,6 +90,18 @@ static unsigned long frame_list[PAGE_SIZ
 #define dec_totalhigh_pages() ((void)0)
 #endif
 
+#ifndef CONFIG_XEN
+/*
+ * In HVM guests accounting here uses the Xen visible values, but the kernel
+ * determined totalram_pages value shouldn't get altered. Since totalram_pages
+ * includes neither the kernel static image nor any memory allocated prior to
+ * or from the bootmem allocator, we have to synchronize the two values.
+ */
+static unsigned long __read_mostly totalram_bias;
+#else
+#define totalram_bias 0
+#endif
+
 /* List of ballooned pages, threaded through the mem_map array. */
 static LIST_HEAD(ballooned_pages);
 
@@ -305,7 +317,7 @@ static int increase_reservation(unsigned
        }
 
        bs.current_pages += rc;
-       totalram_pages = bs.current_pages;
+       totalram_pages = bs.current_pages - totalram_bias;
 
  out:
        balloon_unlock(flags);
@@ -385,7 +397,7 @@ static int decrease_reservation(unsigned
        BUG_ON(ret != nr_pages);
 
        bs.current_pages -= nr_pages;
-       totalram_pages = bs.current_pages;
+       totalram_pages = bs.current_pages - totalram_bias;
 
        balloon_unlock(flags);
 
@@ -524,7 +536,19 @@ static struct notifier_block xenstore_no
 
 static int __init balloon_init(void)
 {
-#if defined(CONFIG_X86) && defined(CONFIG_XEN) 
+#if !defined(CONFIG_XEN)
+# ifndef XENMEM_get_pod_target
+#  define XENMEM_get_pod_target 17
+       typedef struct xen_pod_target {
+               uint64_t target_pages;
+               uint64_t tot_pages;
+               uint64_t pod_cache_pages;
+               uint64_t pod_entries;
+               domid_t domid;
+       } xen_pod_target_t;
+# endif
+       xen_pod_target_t pod_target = { .domid = DOMID_SELF };
+#elif defined(CONFIG_X86)
        unsigned long pfn;
        struct page *page;
 #endif
@@ -538,7 +562,20 @@ static int __init balloon_init(void)
        bs.current_pages = min(xen_start_info->nr_pages, max_pfn);
        totalram_pages   = bs.current_pages;
 #else 
-       bs.current_pages = totalram_pages; 
+       totalram_bias = HYPERVISOR_memory_op(
+               HYPERVISOR_memory_op(XENMEM_get_pod_target,
+                       &pod_target) != -ENOSYS
+               ? XENMEM_maximum_reservation
+               : XENMEM_current_reservation,
+               &pod_target.domid);
+       if ((long)totalram_bias != -ENOSYS) {
+               BUG_ON(totalram_bias < totalram_pages);
+               bs.current_pages = totalram_bias;
+               totalram_bias -= totalram_pages;
+       } else {
+               totalram_bias = 0;
+               bs.current_pages = totalram_pages;
+       }
 #endif
        bs.target_pages  = bs.current_pages;
        bs.balloon_low   = 0;
@@ -671,7 +708,7 @@ struct page **alloc_empty_pages_and_page
                        goto err;
                }
 
-               totalram_pages = --bs.current_pages;
+               totalram_pages = --bs.current_pages - totalram_bias;
 
                balloon_unlock(flags);
        }

Attachment: xenlinux-balloon-hvm-bias.patch
Description: Text document

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