[Xen-devel] Re: HVM hypercalls

[veeruyours <veeruyours@xxxxxxxxx>]

Hi,

I downloaded 2.6.38.7 and seen the CONFIG_XEN_PVHVM available. This feature is automatically selected if XEN and X86_LOCAL_APIC are seletected.

config XEN_PVHVM
ÂÂÂÂÂÂÂ def_bool y
ÂÂÂÂÂÂÂ depends on XEN
ÂÂÂÂÂÂÂ depends on X86_LOCAL_APIC

But, when i select XEN (CONFIG_XEN), it automatically selects "PARAVIRT". Does that make my HVM guest into PV guest?

CONFIG_PARAVIRT:ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 

This changes the kernel so it can modify itself when it is run 
under a hypervisor, potentially improving performance significantly 
over full virtualization. However, when run without a hypervisor the kernel is theoretically slower and slightly larger.

i do not want to convert HVM guest into PV, i just want to make hypercalls from HVM guest to hypervisor.

Could you please suggest.

Thanks & Regards,
VSR.

On Tue, May 24, 2011 at 7:39 PM, Ian Campbell-10 [via Xen] <[hidden email]> wrote:

On Tue, 2011-05-24 at 14:58 +0100, veeruyours wrote:

> I am running 2.6.30 (downloaded from kernel.org) on top of CENTOS 5.4.

That is a very old kernel (June 2009 IIRC).

> Do u mean i should enable following option
>
> --> Processor type and features
> Â Â Â [*] Paravirtualized guest support Â--->
> Â Â Â Â Â Â Â--> [ ] Â Xen guest support (NEW)
>
> But enabling this also selects PARAVIRT and does it make my guest PV
> guest or PVHVM guest?

This kernel only support PV and not PVHVM. You need something newer for
PVHVM, I forget exactly when it was but 2.6.38/39 is certainly new
enough.

Ian.

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