Re: [PATCH] Fix restore handling checks

[Michal Novotny <minovotn@redhat.com>]

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On 06/22/2010 08:17 AM, Michal Novotny wrote:
> On 06/22/2010 08:14 AM, Keir Fraser wrote:
>> Okay, hopefully someone will be able to Ack this patch with better 
>> knwoledge
>> of xend than me.
>>
>>   -- Keir
>>
> Ok, good. If it will be accepted and put into xen-staging/xen-unstable 
> tree please let me know about it.
>
> Thanks,
> Michal
>

Well, this is new version of the patch since I've tried now to both 
migrate from RHEL-5 host (python-2.4) to RHEL-6 host (python-2.6) using 
the RHEL-5 host as a source machine for migrations and also RHEL-6 host 
to restore the the guest locally using `xm restore` to see whether the 
guest memory calculated correctly and it did pass when there was enough 
memory to create the guest and failed when there was not enough memory 
to create the guest. Also, some fixing for comparing the values was 
necessary since it was treated as string comparison on one of the hosts.

Both the host machines were having the latest Xen-4.1 installed.

Michal

Signed-off-by: Michal Novotny <minovotn@redhat.com>

-- 
Michal Novotny<minovotn@redhat.com>, RHCE
Virtualization Team (xen userspace), Red Hat


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diff -r a24dbfcbdf69 tools/python/xen/xend/XendCheckpoint.py
--- a/tools/python/xen/xend/XendCheckpoint.py	Tue Jun 22 07:19:38 2010 +0100
+++ b/tools/python/xen/xend/XendCheckpoint.py	Tue Jun 22 12:52:56 2010 +0200
@@ -64,6 +64,78 @@ def insert_after(list, pred, value):
               list.insert (i+1, value)
     return
 
+def get_avail_memory():
+    """Get available memory for new guest creation (in KiB, for restore)"""
+    from xen.xend import XendOptions
+
+    # First get total memory in KiB
+    xc = xen.lowlevel.xc.xc()
+    info = xc.domain_getinfo()
+    total_mem  = xc.physinfo()['total_memory']
+    del xc
+
+    # Count memory of all running guests in KiB
+    mem_used = 0L
+    for x in info:
+        if x['domid'] != 0:
+            # If blocked & paused & !paused & no online_vcpus we most
+            # probably migrate so we get maxmem instead (since mem_kb
+            # is having currently transferred amount of memory so we
+            # cannot use it for good calculations)
+            if (x['blocked'] == 1 and x['paused'] == 1 and
+                x['running'] == 0 and x['online_vcpus'] == 0):
+                log.debug("Domain %d seems to be restoring" % x['domid'])
+                mem_used += x['maxmem_kb']
+            else:
+                mem_used += x['mem_kb']
+
+    # Get minimal memory for dom0 and convert to KiB
+    min_mem = XendOptions.instance().get_dom0_min_mem() * 1024
+
+    return total_mem - mem_used - min_mem
+
+def check_for_restore_bail(msg):
+    raise VmError("Cannot restore: %s" % msg)
+
+def check_for_enough_mem(val):
+    mem_avail = get_avail_memory() / 1024
+    log.debug("Available memory: %s MiB, guest requires: %s MiB" % (mem_avail, val))
+    return int(mem_avail) > int(val)
+
+def check_for_restore_is_hvm(cfg):
+    for item in cfg:
+        if (type(item) == list):
+           if item[0] == 'image':
+               return type(item[1]) == list and item[1][0] == 'hvm'
+
+def check_for_restore_hvm_have_readonly_ide(cfg):
+    """Check the configuration for read-only IDE devices
+       Fail if such a device is found."""
+    disallow = None
+    if type(cfg) == list and cfg[0] in ('tap', 'vbd'):
+        for p in cfg:
+            if (type(p) != str):
+                if p[0] == 'dev':
+                    disallow = ((p[1].find('hd') >= 0) and
+                                (p[1].find('cdrom') == -1))
+                if p[0] == 'mode' and disallow:
+                    if p[1] == 'r':
+                        return True
+    return False
+
+def check_for_restore(cfg):
+    is_hvm = check_for_restore_is_hvm(cfg)
+    name = None
+    for item in cfg:
+        if (type(item) == list):
+            # Check for enough memory to create the guest
+            if item[0] == 'memory':
+                if not check_for_enough_mem(item[1]):
+                    check_for_restore_bail('Host machine doesn\'t have enough memory to create the guest')
+            # We disable read-only IDE drives only for HVM guests
+            if item[0] == 'device' and is_hvm:
+                if check_for_restore_hvm_have_readonly_ide(item[1]):
+                    check_for_restore_bail('HVM domains cannot be using read-only IDE drives')
 
 def save(fd, dominfo, network, live, dst, checkpoint=False, node=-1):
     from xen.xend import XendDomain
@@ -220,6 +292,7 @@ def restore(xd, fd, dominfo = None, paus
             othervm = xd.domain_lookup_nr(domconfig["uuid"])
         if othervm is not None and othervm.domid is not None: 
             raise VmError("Domain '%s' already exists with ID '%d'" % (domconfig["name_label"], othervm.domid))
+        check_for_restore(vmconfig)
 
     if dominfo:
         dominfo.resume()
diff -r a24dbfcbdf69 tools/python/xen/xend/XendDomainInfo.py
--- a/tools/python/xen/xend/XendDomainInfo.py	Tue Jun 22 07:19:38 2010 +0100
+++ b/tools/python/xen/xend/XendDomainInfo.py	Tue Jun 22 12:52:56 2010 +0200
@@ -82,6 +82,32 @@ log = logging.getLogger("xend.XendDomain
 log = logging.getLogger("xend.XendDomainInfo")
 #log.setLevel(logging.TRACE)
 
+def cfg_is_hvm(cfg):
+    for item in cfg:
+        if (type(item) == list):
+           if item[0] == 'image':
+               return type(item[1]) == list and item[1][0] == 'hvm'
+
+def cfg_hvm_have_readonly_ide_disks(cfg):
+    """Check whether the configuration for read-only IDE disks since
+       they are not supported according to IDE specifications."""
+    if not cfg_is_hvm(cfg):
+        return False
+
+    disallow = None
+    for item in cfg:
+        if (type(item) == list):
+            if item[0] == 'device':
+                if type(item[1]) == list and item[1][0] in ('tap', 'vbd'):
+                    for p in item[1]:
+                        if (type(p) != str):
+                            if p[0] == 'dev':
+                              disallow = ((p[1].find('hd') >= 0) and
+                                          (p[1].find('cdrom') == -1))
+                        if p[0] == 'mode' and disallow:
+                            if p[1] == 'r':
+                                return True
+    return False
 
 def create(config):
     """Creates and start a VM using the supplied configuration. 
@@ -100,6 +126,10 @@ def create(config):
         othervm = XendDomain.instance().domain_lookup_nr(domconfig["uuid"])
     if othervm is not None and othervm.domid is not None:
         raise VmError("Domain '%s' already exists with ID '%d'" % (domconfig["name_label"], othervm.domid))
+
+    if cfg_hvm_have_readonly_ide_disks(config):
+        raise VmError("HVM domains cannot be using read-only IDE drives")
+
     log.debug("XendDomainInfo.create(%s)", scrub_password(config))
     vm = XendDomainInfo(domconfig)
     try:

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