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

On Fri, 6 Jan 2012, Andrew Jones wrote:

----- Original Message -----

quoted

On Fri, 6 Jan 2012, Andrew Jones wrote:

quoted

quoted

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.

quoted

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.

 
The reason to remove is easy: it is already a silent option and
disabling it saves almost nothing.
I think that removing it should be easy enough but if you don't
feel confident doing it, I can come up with a patch.