CentOS - Sep 2016 - How to enable the svm cpu flag inside a vm?

Hello,

I'm trying to get the Android Emulator to run inside a kvm vm on
CentOS-6. Apparently the latest Android Emulators cannot run without
hardware acceleration so I am trying to get the vm to see the svm cpu
flag.

Host:
$ grep model\ name /proc/cpuinfo | sort -u
model name	: AMD Phenom(tm) II X4 965 Processor

$ grep svm /proc/cpuinfo | sort -u
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt
pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nonstop_tsc
extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic
cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt npt
lbrv svm_lock nrip_save

$ cat /sys/module/kvm_amd/parameters/nested 
1

I have tried copying the cpu options (Opteron_G3) in the host cpu
configuration and setting the svm flag to either "model",
"required" or
"force" to no avail:

$ ps waux | grep qemu
qemu      7962  7.2 21.9 3722092 2680668 ?     Rl   13:23
6:36 /usr/libexec/qemu-kvm -name C7-Android -S -M rhel6.6.0 -cpu
Opteron_G3,+invtsc,+wdt,+skinit,+ibs,+osvw,+3dnowprefetch,+cr8legacy,
+extapic,+cmp_legacy,+3dnow,+3dnowext,+pdpe1gb,+fxsr_opt,+mmxext,+ht,
+vme -enable-kvm -m 3072 -realtime mlock=off -smp 
<snip>

So the question is: How do I enable the svm flag in the guest?

Regards,
Leonard.

-- 
mount -t life -o ro /dev/dna /genetic/research

Hi,

On Fri, 2016-09-23 at 15:05 +0200, Leonard den Ottolander
wrote:
> So the question is: How do I enable the svm flag in the guest?
The qemu-kvm option "-enable-nesting" that I dug up in the source
looks
promising. No mention in the man page on either C6 or C7 but it is
mentioned here:
https://www.redhat.com/archives/libvir-list/2012-October/msg01138.html

How do I pass the "-enable-nesting" option to qemu-kvm using either
virt-manager.py, virsh or the domain xml?

Hoping to avoid having to patch the source a such:

--- qemu-kvm-0.12.1.2.000/target-i386/helper.c	2009-12-29 21:46:34.000000000
+0100
+++ qemu-kvm-0.12.1.2/target-i386/helper.c	2016-09-25 16:35:02.984334623 +0200
@@ -1811,8 +1811,10 @@ void cpu_x86_cpuid(CPUX86State *env, uin
             /* disable CPU features that KVM cannot support */
 
             /* svm */
+/*
             if (!kvm_nested)
                 *ecx &= ~CPUID_EXT3_SVM;
+*/
             /* 3dnow */
             *edx &= ~0xc0000000;
         } else {

Regards,
Leonard.

-- 
mount -t life -o ro /dev/dna /genetic/research

On Sun, Sep 25, 2016 at 04:38:39PM +0200, Leonard den Ottolander
wrote:
> The qemu-kvm option "-enable-nesting" that I dug up in the source
looks
> promising. No mention in the man page on either C6 or C7 but it is
> mentioned here:
> https://www.redhat.com/archives/libvir-list/2012-October/msg01138.html
> 
> How do I pass the "-enable-nesting" option to qemu-kvm using
either
> virt-manager.py, virsh or the domain xml?
I saw this in the RHEL 7.3 beta release notes:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7-Beta/html/7.3_Release_Notes/technology_previews_virtualization.html

Nested Virtualization will be a tech preview in RHEL 7.3 Beta, and so
it'll be available after RHEL 7.3 is released and CentOS rebuilds it.

-- 
Jonathan Billings <billings at negate.org>