| 1 |
On 01/08/2013 22:38, Walter Dnes wrote: |
| 2 |
> On Thu, Aug 01, 2013 at 08:41:56AM +0200, Michael Hampicke wrote |
| 3 |
> |
| 4 |
>> You can use march=native on your gentoo hosts, that's no problem, as |
| 5 |
>> long as you don't use it on your guests. That's the hole idea of VMs: |
| 6 |
>> being able to move the virtual machine to another machine, that might be |
| 7 |
>> completely different in terms of hardware. The goal is, to be machine |
| 8 |
>> independent. |
| 9 |
> |
| 10 |
> I want to clarify one item, so please pardon me if it looks like I'm |
| 11 |
> asking the same question over again. Assume that I launch QEMU with |
| 12 |
> "-cpu core2duo" and set "-march=native" in the guest's make.conf. My |
| 13 |
> understanding is that the gcc compiler on the guest will see a core2duo, |
| 14 |
> not the physical i5 cpu on my desktop. |
| 15 |
|
| 16 |
That's correct. Try running this in the guest: |
| 17 |
|
| 18 |
gcc -march=native -Q --help=target | grep march | awk '{print $2}' |
| 19 |
|
| 20 |
> |
| 21 |
> We may be looking at different ways of doing the same thing. You're |
| 22 |
> suggesting "-march=core2" in the guest's make.conf. I'm suggesting |
| 23 |
> "-march=native" in the guest's make.conf, which would pick up the cpu |
| 24 |
> type that QEMU sets (cor2duo). I'm trying to make things simpler, by |
| 25 |
> only having to specify the cpu type once, on the QEMU commandline, and |
| 26 |
> leaving gcc to adapt to the QEMU-specified cpu. |
| 27 |
|
| 28 |
--Kerin |
Archives