From dfdc5b0fc1fdf8c6d122df9578912ed90bfbabb4 Mon Sep 17 00:00:00 2001
Message-Id: <dfdc5b0fc1fdf8c6d122df9578912ed90bfbabb4@dist-git>
From: Peter Krempa <pkrempa@redhat.com>
Date: Thu, 12 Nov 2015 08:40:43 +0100
Subject: [PATCH] qemu: hotplug: Fix mlock limit handling on memory hotplug

https://bugzilla.redhat.com/show_bug.cgi?id=1280420

If mlock is required either due to use of VFIO hostdevs or due to the
fact that it's enabled it needs to be tweaked prior to adding new memory
or after removing a module. Add a helper to determine when it's
necessary and reuse it both on hotplug and hotunplug.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1273491
(cherry picked from commit ec90b34acf7cf7d06a63908c39e21b63382a1967)

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/qemu/qemu_domain.c  | 27 +++++++++++++++++++++++++++
 src/qemu/qemu_domain.h  |  1 +
 src/qemu/qemu_hotplug.c | 41 ++++++++++++++++++++++++++++++++++-------
 3 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 944817d..1f206fa 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -3449,3 +3449,30 @@ qemuDomainGetMlockLimitBytes(virDomainDefPtr def)
 
     return memKB << 10;
 }
+
+
+/**
+ * @def: domain definition
+ *
+ * Returns ture if the locked memory limit needs to be set or updated due to
+ * configuration or passthrough devices.
+ * */
+bool
+qemuDomainRequiresMlock(virDomainDefPtr def)
+{
+    size_t i;
+
+    if (def->mem.locked)
+        return true;
+
+    for (i = 0; i < def->nhostdevs; i++) {
+        virDomainHostdevDefPtr dev = def->hostdevs[i];
+
+        if (dev->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS &&
+            dev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI &&
+            dev->source.subsys.u.pci.backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO)
+            return true;
+    }
+
+    return false;
+}
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index 54e7cd9..32f713b 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -476,5 +476,6 @@ int qemuDomainUpdateCurrentMemorySize(virQEMUDriverPtr driver,
                                       virDomainObjPtr vm);
 
 unsigned long long qemuDomainGetMlockLimitBytes(virDomainDefPtr def);
+bool qemuDomainRequiresMlock(virDomainDefPtr def);
 
 #endif /* __QEMU_DOMAIN_H__ */
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index d96f572..70aece4 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -1768,6 +1768,7 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver,
     virJSONValuePtr props = NULL;
     virObjectEventPtr event;
     bool fix_balloon = false;
+    bool mlock = false;
     int id;
     int ret = -1;
 
@@ -1802,16 +1803,26 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver,
         goto cleanup;
     }
 
+    mlock = qemuDomainRequiresMlock(vm->def);
+
+    if (mlock &&
+        virProcessSetMaxMemLock(vm->pid,
+                                qemuDomainGetMlockLimitBytes(vm->def)) < 0) {
+        mlock = false;
+        virJSONValueFree(props);
+        goto removedef;
+    }
+
     qemuDomainObjEnterMonitor(driver, vm);
     if (qemuMonitorAddObject(priv->mon, backendType, objalias, props) < 0)
-        goto removedef;
+        goto exit_monitor;
 
     if (qemuMonitorAddDevice(priv->mon, devstr) < 0) {
         virErrorPtr err = virSaveLastError();
         ignore_value(qemuMonitorDelObject(priv->mon, objalias));
         virSetError(err);
         virFreeError(err);
-        goto removedef;
+        goto exit_monitor;
     }
 
     if (qemuDomainObjExitMonitor(driver, vm) < 0) {
@@ -1846,17 +1857,27 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver,
     virDomainMemoryDefFree(mem);
     return ret;
 
+ exit_monitor:
+    if (qemuDomainObjExitMonitor(driver, vm) < 0) {
+        mem = NULL;
+        goto audit;
+    }
+
  removedef:
-    if (qemuDomainObjExitMonitor(driver, vm) < 0) {
-        mem = NULL;
-        goto audit;
-    }
-
     if ((id = virDomainMemoryFindByDef(vm->def, mem)) >= 0)
         mem = virDomainMemoryRemove(vm->def, id);
     else
         mem = NULL;
 
+    /* reset the mlock limit */
+    if (mlock) {
+        virErrorPtr err = virSaveLastError();
+        ignore_value(virProcessSetMaxMemLock(vm->pid,
+                                             qemuDomainGetMlockLimitBytes(vm->def)));
+        virSetError(err);
+        virFreeError(err);
+    }
+
     goto audit;
 }
 
@@ -2952,6 +2973,12 @@ qemuDomainRemoveMemoryDevice(virQEMUDriverPtr driver,
         virDomainMemoryRemove(vm->def, idx);
 
     virDomainMemoryDefFree(mem);
+
+    /* decrease the mlock limit after memory unplug if necessary */
+    if (qemuDomainRequiresMlock(vm->def))
+        ignore_value(virProcessSetMaxMemLock(vm->pid,
+                                             qemuDomainGetMlockLimitBytes(vm->def)));
+
     return 0;
 }
 
-- 
2.6.3