Re: [libvirt] PATCH: recent qemu-kvm requires -enable-kvm flag to activate VT optimization

[Steve Yarmie <steve.yarmie@xxxxxxxxx>]

Right - I left it out of the patch by mistake. New attachment has the needed test: 

+    if (strstr(help, "-enable-kvm"))                                                                                                                                  
+        flags |= QEMUD_CMD_FLAG_ENABLEKVM;

-Steve

Daniel Veillard wrote:

On Sun, Nov 15, 2009 at 07:03:51PM -0800, Steve Yarmie wrote:
  

Hello,

Recent qemu releases require command option '-enable-qemu' in order
for the kvm functionality be activated. Libvirt needs to pass this flag 
to qemu when starting a domain. Note that without the option,
even if both the kernel and qemu support KVM, KVM will not be activated
and VMs will be slow as molasses ;)

I added a check in qemu_conf.c to see if `qemu -help` emits the -enable-kvm
flag, and if so, use the flag accordingly.

There exists a check in src/qemu/qemu_conf.c to check for the -no-kvm flag.
This check works the same way. 

Adding the included code will not break systems where qemu does not
have the option.

See 'qemu -help':
...
-enable-kvm     enable KVM full virtualization support ...

included patch against src/qemu/qemu_conf.{c,h}  

-Steve


    

diff -ur libvirt/src/qemu/qemu_conf.c libvirt-qemu-enable-kvm/src/qemu/qemu_conf.c
--- libvirt/src/qemu/qemu_conf.c	2009-11-08 20:57:08.438908134 -0800
+++ libvirt-qemu-enable-kvm/src/qemu/qemu_conf.c	2009-11-08 22:36:04.299921427 -0800
@@ -1602,6 +1602,7 @@
     struct utsname ut;
     int disableKQEMU = 0;
     int disableKVM = 0;
+    int enableKVM = 0;
     int qargc = 0, qarga = 0;
     const char **qargv = NULL;
     int qenvc = 0, qenva = 0;
@@ -1660,6 +1661,15 @@
         def->virtType == VIR_DOMAIN_VIRT_QEMU)
         disableKVM = 1;
 
+    /* Should explicitly enable KVM if
+     * 1. Guest domain is 'qemu'
+     * 2. The qemu binary has the -enable-kvm flag
+     * NOTE: user must be responsible to load the kvm modules
+     */
+    if ((qemuCmdFlags & QEMUD_CMD_FLAG_ENABLE_KVM) &&
+        def->virtType == VIR_DOMAIN_VIRT_QEMU)
+        enableKVM = 1;
+
     /*
      * Need to force a 32-bit guest CPU type if
      *
@@ -1787,6 +1797,8 @@
         ADD_ARG_LIT("-no-kqemu");
     if (disableKVM)
         ADD_ARG_LIT("-no-kvm");
+    if (enableKVM)
+	ADD_ARG_LIT("-enable-kvm");
     ADD_ARG_LIT("-m");
     ADD_ARG_LIT(memory);
     if (def->hugepage_backed) {
diff -ur libvirt/src/qemu/qemu_conf.h libvirt-qemu-enable-kvm/src/qemu/qemu_conf.h
--- libvirt/src/qemu/qemu_conf.h	2009-11-08 20:57:08.438908134 -0800
+++ libvirt-qemu-enable-kvm/src/qemu/qemu_conf.h	2009-11-08 14:57:39.000000000 -0800
@@ -73,6 +73,7 @@
     QEMUD_CMD_FLAG_XEN_DOMID     = (1 << 20), /* -xen-domid (new style xen integration) */
     QEMUD_CMD_FLAG_MIGRATE_QEMU_UNIX = (1 << 21), /* Does qemu support unix domain sockets for migration? */
     QEMUD_CMD_FLAG_CHARDEV       = (1 << 22), /* Is the new -chardev arg available */
+    QEMUD_CMD_FLAG_ENABLE_KVM    = (1 << 23), /* Is the -enable-kvm flag available to "enable KVM full virtualization support" */
 };
 
 /* Main driver state */
    

 Patch seems incomplete as I don't see any detection code setting up
QEMUD_CMD_FLAG_ENABLE_KVM in qemuCmdFlags

Daniel

  

diff -upr libvirt/src/qemu/qemu_conf.c libvirt-enableKVM/src/qemu/qemu_conf.c
--- libvirt/src/qemu/qemu_conf.c	2009-11-15 18:23:34.132206179 -0800
+++ libvirt-enableKVM/src/qemu/qemu_conf.c	2009-11-16 01:56:08.519182637 -0800
@@ -878,6 +878,8 @@ static unsigned int qemudComputeCmdFlags
         flags |= QEMUD_CMD_FLAG_KQEMU;
     if (strstr(help, "-no-kvm"))
         flags |= QEMUD_CMD_FLAG_KVM;
+    if (strstr(help, "-enable-kvm"))
+        flags |= QEMUD_CMD_FLAG_ENABLEKVM;
     if (strstr(help, "-no-reboot"))
         flags |= QEMUD_CMD_FLAG_NO_REBOOT;
     if (strstr(help, "-name"))
@@ -1595,6 +1597,7 @@ int qemudBuildCommandLine(virConnectPtr 
     struct utsname ut;
     int disableKQEMU = 0;
     int disableKVM = 0;
+    int enableKVM = 0;
     int qargc = 0, qarga = 0;
     const char **qargv = NULL;
     int qenvc = 0, qenva = 0;
@@ -1653,6 +1656,15 @@ int qemudBuildCommandLine(virConnectPtr 
         def->virtType == VIR_DOMAIN_VIRT_QEMU)
         disableKVM = 1;
 
+    /* Should explicitly enable KVM if
+     * 1. Guest domain is 'qemu'
+     * 2. The qemu binary has the -enable-kvm flag
+     * NOTE: user must be responsible to load the kvm modules
+     */
+    if ((qemuCmdFlags & QEMUD_CMD_FLAG_ENABLE_KVM) &&
+        def->virtType == VIR_DOMAIN_VIRT_QEMU)
+        enableKVM = 1;
+
     /*
      * Need to force a 32-bit guest CPU type if
      *
@@ -1780,6 +1792,8 @@ int qemudBuildCommandLine(virConnectPtr 
         ADD_ARG_LIT("-no-kqemu");
     if (disableKVM)
         ADD_ARG_LIT("-no-kvm");
+    if (enableKVM)
+	ADD_ARG_LIT("-enable-kvm");
     ADD_ARG_LIT("-m");
     ADD_ARG_LIT(memory);
     if (def->hugepage_backed) {
diff -upr libvirt/src/qemu/qemu_conf.h libvirt-enableKVM/src/qemu/qemu_conf.h
--- libvirt/src/qemu/qemu_conf.h	2009-11-15 18:23:34.136206610 -0800
+++ libvirt-enableKVM/src/qemu/qemu_conf.h	2009-11-16 01:50:54.830156632 -0800
@@ -73,6 +73,7 @@ enum qemud_cmd_flags {
     QEMUD_CMD_FLAG_XEN_DOMID     = (1 << 20), /* -xen-domid (new style xen integration) */
     QEMUD_CMD_FLAG_MIGRATE_QEMU_UNIX = (1 << 21), /* Does qemu support unix domain sockets for migration? */
     QEMUD_CMD_FLAG_CHARDEV       = (1 << 22), /* Is the new -chardev arg available */
+    QEMUD_CMD_FLAG_ENABLE_KVM    = (1 << 23), /* Is the -enable-kvm flag available to "enable KVM full virtualization support" */
 };
 
 /* Main driver state */

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