Re: [Xen-devel] [PATCH] docs: add vpmu description to xen-command-line.markdown

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-04-27 at 10:20 +0100, Dietmar Hahn wrote:
> # HG changeset patch
> # User Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
> # Date 1335517766 -7200
> # Node ID 9ba4e4a5f3b1b7dad77e2801afc0253d6d30d565
> # Parent  107285938c50f82667bd4d014820b439a077c22c
> 
> Add a short description to the vpmu boot option in the
> xen-command-line.markdown
> 
> 
> Signed-off-by:  Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>

Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Can't we just blacklist systems with the nehalem quirk and otherwise
enable it?

Ian.

> 
> 
> diff -r 107285938c50 docs/misc/xen-command-line.markdown
> --- a/docs/misc/xen-command-line.markdown     Thu Apr 26 10:03:08 2012 +0100
> +++ b/docs/misc/xen-command-line.markdown     Fri Apr 27 11:09:26 2012 +0200
> @@ -543,7 +543,28 @@ console even after dom0 has been started
>  relinquish control to dom0.
>  
>  ### vpid
> +
>  ### vpmu
> +> `= ( bts )`
> +
> +> Default: `off`
> +
> +Switch on the virtualized performance monitoring unit for HVM guests.
> +
> +If the current cpu isn't supported a message like  
> +'VPMU: Initialization failed. ...'  
> +is printed on the hypervisor serial log.
> +
> +For some Intel Nehalem processors a quirk handling exist for an unknown
> +wrong behaviour (see handle_pmc_quirk()).
> +
> +If 'vpmu=bts' is specified the virtualisation of the Branch Trace Store (BTS)
> +feature is switched on on Intel processors supporting this feature.
> +
> +*Warning:*
> +As the BTS virtualisation is not 100% safe and because of the nehalem quirk
> +don't use the vpmu flag on production systems with Intel cpus!
> +
>  ### vti\_vhpt\_size
>  ### vti\_vtlb\_size
>  ### watchdog
> 
> 



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