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

[Steve Yarmie]

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
>
>   

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