Re: [Xen-devel] [PATCH 3/4] xen kconfig: add dom0 support help text

[Andrew Jones <drjones@xxxxxxxxxx>]

----- Original Message -----
> On Fri, 6 Jan 2012, Andrew Jones wrote:
> > > Almost all of the things which dom0 needs (e.g. PCI device
> > > management
> > > etc) is also required by a domU with passthrough enabled so the
> > > savings
> > > are really very slight.
> > > 
> > > We are talking less than 1k of code AFAICT, 319 bytes for
> > > arch/x86/xen/vga.o and 573 for drivers/xen/xenfs/xenstored.o plus
> > > whatever xen_register_gsi (a couple of dozen lines of code) adds
> > > to
> > > arch/x86/pci/xen.o. grep doesn't show CONFIG_XEN_DOM0 being used
> > > anywhere else. What savings do you see in practice from disabling
> > > just
> > > this symbol?
> > 
> > I completely agree that the saving are near none. The savings,
> > however,
> > aren't the only reason to drive the change. It's actually the
> > symbol
> > name itself. Unfortunately configs can be perceived as a contract
> > of
> > support, i.e. if feature xyz is enabled in the distro's config,
> > then
> > the distributor must have selected, and therefore will support,
> > said
> > feature.
> > 
> > I didn't make this motivation clear in my initial post, because I
> > was
> > hoping to spare people some eye rolling.
> 
> I thought that in the kernel community we make decisions based on
> technical merits rather than "contracts of support".

Sorry.

> Given that disabling the symbol saves near to nothing, the logical
> thing
> to do is removing the symbol altogether.
> 

I thought of that too. If the symbol just goes away, then my
non-technical requirement will be met and the functionality will
stay. I consider that a bigger win actually. I didn't suggest it
though, since I've never done any dom0 development, nor had any
consideration for dom0 code needs of the future. With
anti-credentials like that, I'd guess it'd be tougher for me to sell
the need to remove it, than it is for me to just make it
configurable.

Drew

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