[libvirt] getFreeMemory reporting incorrectly?

[Daniel P. Berrange]

On Thu, Jun 11, 2009 at 02:37:57PM -0400, Hany Fahim wrote:
> Thanks Daniel,
> Is it fair to assume this fix may appear in the next release of libvirt?

If you want to build from source, I'd appreciate feedback on whether
the following patch fixes the problem

diff -r f204769dd197 src/xen_internal.c
--- a/src/xen_internal.c	Wed Jun 03 13:52:06 2009 +0000
+++ b/src/xen_internal.c	Fri Jun 12 15:44:05 2009 +0100
@@ -241,6 +241,15 @@ struct xen_v2s4_availheap {
 
 typedef struct xen_v2s4_availheap  xen_v2s4_availheap;
 
+struct xen_v2s5_availheap {
+    uint32_t min_bitwidth;  /* Smallest address width (zero if don't care). */
+    uint32_t max_bitwidth;  /* Largest address width (zero if don't care). */
+    int32_t  node;          /* NUMA node (-1 for sum across all nodes). */
+    uint64_t avail_bytes ALIGN_64;   /* Bytes available in the specified region. */
+};
+
+typedef struct xen_v2s5_availheap  xen_v2s5_availheap;
+
 
 #define XEN_GETDOMAININFOLIST_ALLOC(domlist, size)                      \
     (hypervisor_version < 2 ?                                           \
@@ -650,6 +659,7 @@ struct xen_op_v2_sys {
         xen_v2s3_getdomaininfolistop getdomaininfolists3;
         xen_v2_getschedulerid        getschedulerid;
         xen_v2s4_availheap           availheap;
+        xen_v2s5_availheap           availheap5;
         uint8_t padding[128];
     } u;
 };
@@ -3125,12 +3135,18 @@ xenHypervisorNodeGetCellsFreeMemory(virC
     op_sys.cmd = XEN_V2_OP_GETAVAILHEAP;
 
     for (i = startCell, j = 0;(i < priv->nbNodeCells) && (j < maxCells);i++,j++) {
-        op_sys.u.availheap.node = i;
+        if (sys_interface_version >= 5)
+            op_sys.u.availheap5.node = i;
+        else
+            op_sys.u.availheap.node = i;
         ret = xenHypervisorDoV2Sys(priv->handle, &op_sys);
         if (ret < 0) {
             return(-1);
         }
-        freeMems[j] = op_sys.u.availheap.avail_bytes;
+        if (sys_interface_version >= 5)
+            freeMems[j] = op_sys.u.availheap5.avail_bytes;
+        else
+            freeMems[j] = op_sys.u.availheap.avail_bytes;
     }
     return (j);
 }



> >
> >
> > This shows that the Hypervisor  is giving correct info back with both
> > versions. So the problem must be at the libvirt space, and I believe
> > I know what the problem is.
> >
> > The version of Xen in RHEL5 has
> >
> > struct xen_sysctl_availheap {
> >    /* IN variables. */
> >    uint32_t min_bitwidth;  /* Smallest address width (zero if don't care).
> > */
> >    uint32_t max_bitwidth;  /* Largest address width (zero if don't care).
> > */
> >    int32_t  node;          /* NUMA node of interest (-1 for all nodes). */
> >    /* OUT variables. */
> >    uint64_t avail_bytes;   /* Bytes available in the specified region. */
> > };
> >
> > While upstream Xen has
> >
> > struct xen_sysctl_availheap {
> >    /* IN variables. */
> >    uint32_t min_bitwidth;  /* Smallest address width (zero if don't care).
> > */
> >    uint32_t max_bitwidth;  /* Largest address width (zero if don't care).
> > */
> >    int32_t  node;          /* NUMA node of interest (-1 for all nodes). */
> >    /* OUT variables. */
> >    uint64_aligned_t avail_bytes;/* Bytes available in the specified region.
> > */
> > };
> >
> > Notice the 'avail_bytes' field is now aligned, so its 4 bytes further
> > down from where libvirt is expecting it to be.
> >
> > We'll have to provide a fix in libvirt to use the new alignment for
> > newer Xen.

Daniel
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