RE: [Xen-devel] VT-x and frontend/backend drivers

["Yu, Ke" <ke.yu@xxxxxxxxx>]

Mark Ryden wrote:
> Hello,
> 
>   As I saw in this mailing list, there should be some
>       emulation solution for drivers when using VT-x processors.
> 
> See for example :
>
http://lists.xensource.com/archives/html/xen-devel/2005-12/msg00763.html
> 
> My question is this;
> 
>   As I understand, the VMX support in the new  VT-x processors
> enables us to prevent Guest OSs from performing
> unwanted instructions (HLT , for example). This is
> done by using the root and non-root VMX operation.
>  Thus , we don't use paravirtualization and we
> can run unmodified guest.
>   Is there a possibility or any intention of using the
> backend-frontend solution of Xen (maybe with some fixes) when using
> VT-x processors ? wouldn't it be much better in terms of
> performance than using hardware emulation (based on QEMU maybe)?

Agree :) . This is a good way to improve VMX  domain performance.

Idealy, if we can implement the xen infrastructure (e.g. hypercall,
event channel, memory map etc.) in kernel module, porting those
frontend/backend drivers should be easy and may be only small
modification.

One challenge is the hypercall parameter passing.  In DomU case,
hypervisor can use copy_from_user/copy_to_user to pass hypercall
parameter, since they are in the same address space. In VMX domain case,
the domain use different address space than hypervisor, so the
copy_**_user doesn't work. 

Best Regards
Ke
> 
> Regards,
>       --MR
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel