EXPERIMENTAL Report maxmem and fix get_mem variants

Add "maxmem" property to "Qubes" (app) and "AdminVM", so clients can now
system/host memory and dom0 memory.

Fix "get_mem" and "get_mem_static_max" mess:

- AdminVM:
  - "get_mem": supposedly, should report usage in KiB, but it's reading
    /proc/meminfo and returning kB
  - "get_mem_static_max": returning total host memory
- QubesVM:
  - "get_mem": supposedly, should report usage, but it's
    reporting initial memory
  - "get_mem_static_max": same as above

Now all of these methods returns memory in KiB. "get_mem" returns
allocated/assigned memory, while "get_mem_static_max" returns maxmem in
KiB.

Author: ben-grande

qubes/app.py

@@ -899,6 +899,11 @@ def get_qube_prop_deps(
     return system_deps, qube_deps
 
 
+def _default_maxmem(self) -> int:
+    """Get maximum memory available to the whole system."""
+    return self.host.memory_total
+
+
 class Qubes(qubes.PropertyHolder):
     """Main Qubes application
 
@@ -1145,6 +1150,15 @@ class Qubes(qubes.PropertyHolder):
         doc="Check for updates inside qubes",
     )
 
+    maxmem = qubes.property(
+        "maxmem",
+        type=int,
+        setter=qubes.property.forbidden,
+        load_stage=3,
+        default=_default_maxmem,
+        doc="Maximum system memory",
+    )
+
     def __init__(
         self, store=None, load=True, offline_mode=None, lock=False, **kwargs
     ):

qubes/vm/adminvm.py

@@ -25,6 +25,8 @@
 import grp
 import subprocess
 import libvirt
+import lxml
+import lxml.etree
 import uuid
 
 import qubes
@@ -33,6 +35,30 @@
 from qubes.vm.qubesvm import _setter_denied_list, _setter_kbd_layout
 from qubes.vm import LocalVM, BaseVM
 
+def _default_maxmem(self):
+    if self.app.vmm.offline_mode:
+        # default value passed on xen cmdline
+        return 4096
+    try:
+        # Faster to use Xen than to query the fetch the full XML. If one could
+        # find a libvirt method instead of XMLDesc to get the same value as
+        # static-max, that would help.
+        if self.app.vmm.is_xen:
+            val = self.app.vmm.xs.read("", "/local/domain/0/memory/static-max")
+            if not isinstance(val, bytes):
+                raise TypeError("xenstore key static-max is not set")
+            val = val.decode()
+        else:
+            xml = lxml.etree.fromstring(self.libvirt_domain.XMLDesc())
+            val = xml.findtext("currentMemory")
+        if val is None:
+            raise TypeError("not set")
+        if not val.isdigit():
+            raise ValueError("not a digit")
+        return int(val // 1024)
+    except (TypeError, ValueError, libvirt.libvirtError) as e:
+        self.log.warning("Failed to get maxmem for dom0: %s", e)
+        return 4096
 
 class AdminVM(LocalVM):
     """Dom0"""
@@ -95,6 +121,14 @@ class AdminVM(LocalVM):
         doc="Keyboard layout for this VM",
     )
 
+    maxmem = qubes.property(
+        "maxmem",
+        type=int,
+        setter=qubes.property.forbidden,
+        default=_default_maxmem,
+        doc="""Maximum amount of memory available for this VM""",
+    )
+
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
@@ -176,37 +210,30 @@ def get_power_state():
         """
         return "Running"
 
-    @staticmethod
-    def get_mem():
-        """Get current memory usage of Dom0.
-
-        Unit is KiB.
+    def get_mem(self):
+        """Get memory assigned to VM.
 
-        .. seealso:
-           :py:meth:`qubes.vm.qubesvm.QubesVM.get_mem`
+        :returns: Memory assigned in KiB.
         """
-
-        # return psutil.virtual_memory().total/1024
-        with open("/proc/meminfo", encoding="ascii") as file:
-            for line in file:
-                if line.startswith("MemTotal:"):
-                    return int(line.split(":")[1].strip().split()[0])
-        raise NotImplementedError()
+        if self.libvirt_domain is None:
+            return 0
+        try:
+            if not self.libvirt_domain.isActive():
+                return 0
+            return self.libvirt_domain.memoryStats()["actual"]
+        except libvirt.libvirtError as e:
+            self.log.exception(
+                "libvirt error code: {!r}".format(e.get_error_code())
+            )
+            raise
 
     def get_mem_static_max(self):
         """Get maximum memory available to Dom0.
 
         .. seealso:
            :py:meth:`qubes.vm.qubesvm.QubesVM.get_mem_static_max`
         """
-        if self.app.vmm.offline_mode:
-            # default value passed on xen cmdline
-            return 4096
-        try:
-            return self.app.vmm.libvirt_conn.getInfo()[1]
-        except libvirt.libvirtError as e:
-            self.log.warning("Failed to get memory limit for dom0: %s", e)
-            return 4096
+        return self.maxmem * 1024
 
     def get_cputime(self):
         """Get total CPU time burned by Dom0 since start.

qubes/vm/qubesvm.py

@@ -2595,20 +2595,17 @@ def on_domain_is_fully_usable(self, event):
     # memory and disk
 
     def get_mem(self):
-        """Get current memory usage from VM.
+        """Get memory assigned to VM.
 
-        :returns: Memory usage [FIXME unit].
-        :rtype: FIXME
+        :returns: Memory assigned in KiB.
+        :rtype: int
         """
-
         if self.libvirt_domain is None:
             return 0
-
         try:
             if not self.libvirt_domain.isActive():
                 return 0
-            return self.libvirt_domain.info()[1]
-
+            return self.libvirt_domain.memoryStats()["actual"]
         except libvirt.libvirtError as e:
             if e.get_error_code() in (
                 # qube no longer exists
@@ -2617,7 +2614,6 @@ def get_mem(self):
                 libvirt.VIR_ERR_INTERNAL_ERROR,
             ):
                 return 0
-
             self.log.exception(
                 "libvirt error code: {!r}".format(e.get_error_code())
             )
@@ -2626,29 +2622,10 @@ def get_mem(self):
     def get_mem_static_max(self):
         """Get maximum memory available to VM.
 
-        :returns: Memory limit [FIXME unit].
-        :rtype: FIXME
+        :returns: Memory limit in KiB.
+        :rtype: int
         """
-
-        if self.libvirt_domain is None:
-            return 0
-
-        try:
-            return self.libvirt_domain.maxMemory()
-
-        except libvirt.libvirtError as e:
-            if e.get_error_code() in (
-                # qube no longer exists
-                libvirt.VIR_ERR_NO_DOMAIN,
-                # libxl_domain_info failed (race condition from isActive)
-                libvirt.VIR_ERR_INTERNAL_ERROR,
-            ):
-                return 0
-
-            self.log.exception(
-                "libvirt error code: {!r}".format(e.get_error_code())
-            )
-            raise
+        return self.maxmem * 1024
 
     def get_cputime(self):
         """Get total CPU time burned by this domain since start.