Re: [Xen-devel] Re: HVM hypercalls

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-05-25 at 08:38 +0100, veeruyours wrote:
> 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
>         def_bool y
>         depends on XEN
>         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?

No. It makes your kernel capable of being used as either PV, PVHVM or
just HVM kernel. The guest type is purely derived from the guest cfg
file you use.

PV vs PVHVM/HVM is controlled by specifying hvm=0|1. PVHVM vs HVM is
controlled via the xen_platform_device=0|1 option, disabling the
platform device (it is enabled by default) puts you back to just HVM
mode.

BTW, this sort of question really belongs on xen-users.

Ian.

> 
> CONFIG_PARAVIRT:                                                              
>                                                          
> 
> 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 
>         >       [*] Paravirtualized guest support  ---> 
>         >              --> [ ]   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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> 
> ______________________________________________________________________
> View this message in context: Re: HVM hypercalls
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