Re: [Xen-devel] [PATCH v2 3/3] tmem: allow tmem to be disabled with Kconfig

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Mar 16, 2016 at 02:39:02AM -0600, Jan Beulich wrote:
> >>> On 16.03.16 at 08:35, <konrad.wilk@xxxxxxxxxx> wrote:
> > On Tue, Mar 15, 2016 at 03:18:50PM -0500, Doug Goldstein wrote:
> >> Wrap the various tmem functions with the Kconfig generated CONFIG_TMEM
> >> option allowing users to build Xen without tmem support.
> > 
> > I ended with this change on top of yours (which I will squash):
> > 
> > The 'bool "tmem" so that if I did make an change in .config
> > file it would still take effect even if I forgot XEN_CONFIG_EXPERT.
> > 
> > Otherwise it would keep on making it
> > 
> > CONFIG_TMEM=y
> > instead of the
> > 
> > # CONFIG_TMEM is not set.
> > 
> > which I wrote in the .config file.
> > 
> > From b9d173eb0e0e1274c784fde5580b119d6f7b4bdc Mon Sep 17 00:00:00 2001
> > From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > Date: Wed, 16 Mar 2016 03:28:39 -0400
> > Subject: [PATCH] squash!     tmem: allow tmem to be disabled with Kconfig
> > 
> > ---
> >  xen/common/Kconfig | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> > index 39b0fa7..5bd8a84 100644
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -87,16 +87,21 @@ config LATE_HWDOM
> >  
> >       If unsure, say N.
> >  
> > -# Enables transactional memory support
> > +# Enables transcendent memory support
> >  config TMEM
> >     def_bool y
> > -   prompt "Transactional Memory Support" if EXPERT = "y"
> > +   bool "tmem"
> > +   prompt "Transcendent Memory Support" if EXPERT = "y"
> >     ---help---
> >       Transcendent memory allows PV-aware guests to collaborate on memory
> >       usage. Guests can 'swap' their memory to the hypervisor or have an
> >       collective pool of memory shared across guests. The end result is
> >       less memory usage by guests allowing higher guest density.
> >  
> > +     You also have to enable it on the Xen commandline by using tmem=1
> > +
> > +     If unsure, say Y.
> 
> But that will, afaict, disable tmem by default. Forgetting to set

You are correct. I didn't clear my tree to test that. Removing that
bool "tmem".

> XEN_CONFIG_EXPERT is, well, a mistake that results in a config
> change just like the one you've observed.
> 
> Jan
> 

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