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Re: [libvirt] (how much) support for kqemu domain



Hello Eric.

I am fairly sure I remember *someone* saying they had integrated a modified version of the fix into libvirt but can't find any email saying so now. Maybe Daniel? On a very quick look at 0.9.2 source, it *appears* to have been implemented in qemu_command.c (but I didn't verify running it).

Cheers,  John Lumby

On 06/06/11 13:49, Eric Blake wrote:
[digging through old mail]

On 07/17/2010 10:58 AM, John Lumby wrote:
I am wondering about
  the extent to which "old" qemu-0.11.1
and kqemu-1.4.0 are
supported by virt-manager.

It looks for presence of /dev/kqemu and a -no-kqemu arg in

  QEMU's help. I had no idea that arg had been changed to
be
-enable-kqemu.  Patches welcome to support that new
arg. See
qemudBuildCommandLine()&  qemudComputeCmdFlags()
methods in
src/qemu/qemu_conf.c
Daniel

Thanks Daniel for the pointer to the source code .    Interesting "interface".

Here's my patch  -  works for me but tested only on my own qemu-1.11.1
I never saw a reply to this.  Is this a patch that should be revived and
rebased onto the latest git?

--- src/qemu/qemu_conf.h.orig    2010-04-23 11:52:47.000000000 -0400
+++ src/qemu/qemu_conf.h    2010-07-15 15:27:44.000000000 -0400
@@ -88,6 +88,13 @@ enum qemud_cmd_flags {
      QEMUD_CMD_FLAG_NO_HPET       = (1LL<<  33), /* -no-hpet flag is supported */
      QEMUD_CMD_FLAG_NO_KVM_PIT    = (1LL<<  34), /* -no-kvm-pit-reinjection supported */
      QEMUD_CMD_FLAG_TDF           = (1LL<<  35), /* -tdf flag (user-mode pit catchup) */
+
+    /* features added in qemu-0.11.x   jel  */
+    QEMUD_CMD_FLAG_KQEMU_EXPLICIT = (1LL<<  36) /* KQEMU is available but must be explicitly requested
+                                                ** using options  -enable-kqemu -kernel-kqemu
+                                                ** note we either specify both or neither
+                                                **      since qemu domain is always system mode (I think?) jel
+                                                */
  };

  /* Main driver state */
--- src/qemu/qemu_conf.c.orig    2010-04-30 08:46:09.000000000 -0400
+++ src/qemu/qemu_conf.c    2010-07-15 21:15:12.000000000 -0400
@@ -1130,6 +1130,14 @@ static unsigned long long qemudComputeCm

      if (strstr(help, "-no-kqemu"))
          flags |= QEMUD_CMD_FLAG_KQEMU;
+    /*  here we check for qemu version of *exactly* 0.11.x,
+    **  which requires different options to select kqemu      jel  */
+    if (     ( version>= 11000 )&&  ( version<= 11999 )
+&&   (      ( strstr(help, "-enable-kqemu") )
+                 || ( strstr(help, "-kernel-kqemu") )
+             )
+       )
+      flags |= ( QEMUD_CMD_FLAG_KQEMU | QEMUD_CMD_FLAG_KQEMU_EXPLICIT );
      if (strstr(help, "-no-kvm"))
          flags |= QEMUD_CMD_FLAG_KVM;
      if (strstr(help, "-enable-kvm"))
@@ -3431,7 +3439,10 @@ int qemudBuildCommandLine(virConnectPtr
      char memory[50];
      char boot[VIR_DOMAIN_BOOT_LAST];
      struct utsname ut;
-    int disableKQEMU = 0;
+    int disableKQEMU = 0;           /*   0 means don't enable or disable
+                                    **  +1 means do explicitly disable
+                                    **  -1 means do explicitly enable (double-negative)
+                                    */
      int disableKVM = 0;
      int enableKVM = 0;
      int qargc = 0, qarga = 0;
@@ -3484,10 +3495,24 @@ int qemudBuildCommandLine(virConnectPtr
      /* Need to explicitly disable KQEMU if
       * 1. Guest domain is 'qemu'
       * 2. The qemu binary has the -no-kqemu flag
+     *
+     * and need to explicitly enable KQEMU if
+     * 1. Guest domain is 'kqemu'
+     * 2. The qemu binary has the -enable-kqemu flag
       */
-    if ((qemuCmdFlags&  QEMUD_CMD_FLAG_KQEMU)&&
-        def->virtType == VIR_DOMAIN_VIRT_QEMU)
-        disableKQEMU = 1;
+
+    if (qemuCmdFlags&  QEMUD_CMD_FLAG_KQEMU) {
+      /*  we need to decide whether to explictly enable,
+      ** explicitly disable, or neither (default) */
+      if (def->virtType == VIR_DOMAIN_VIRT_QEMU) {
+            disableKQEMU = 1;
+      } else
+      if (    ( def->virtType == VIR_DOMAIN_VIRT_KQEMU )
+&&  ( qemuCmdFlags&  QEMUD_CMD_FLAG_KQEMU_EXPLICIT )
+         ) {
+            disableKQEMU = -1;    /*  explicitly enable */
+      }
+    }

      /* Need to explicitly disable KVM if
       * 1. Guest domain is 'qemu'
@@ -3617,8 +3642,12 @@ int qemudBuildCommandLine(virConnectPtr
          VIR_FREE(cpu);
      }

-    if (disableKQEMU)
+    if (disableKQEMU == 1)
          ADD_ARG_LIT("-no-kqemu");
+    else if (disableKQEMU == -1) {
+        ADD_ARG_LIT("-enable-kqemu");
+        ADD_ARG_LIT("-kernel-kqemu");
+    }
      if (disableKVM)
          ADD_ARG_LIT("-no-kvm");
      if (enableKVM)




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