Re: [Xen-devel] [PATCH v5.99.1 RFC 1/4] xen/arm: Duplicate gic-v2.c file to support hip04 platform version

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 26 Feb 2015, Ian Campbell wrote:
> On Wed, 2015-02-25 at 16:34 +0000, Stefano Stabellini wrote:
> > I think we should disable the build of all drivers in Xen by default,
> > except for the ARM standard compliant ones (for aarch64 the SBSA is a
> > nice summary of what is considered compliant), to keep the size of the
> > binary small.
> 
> I think this last statement was based on information that the gic-v2
> driver was of the order of 70-100K in size, but I think that information
> was wrong (I suspect it was the raw .o size, which includes debug info
> and other extraneous bits). Here I see:
> 
> $ du -h xen/arch/arm/gic-v2.o
> 148K  xen/arch/arm/gic-v2.o
> $ aarch64-linux-gnu-size xen/arch/arm/gic-v2.o 
>    text          data     bss     dec     hex filename
>    6619             0      97    6716    1a3c xen/arch/arm/gic-v2.o
> 
> IOW the actual binary size is on the order of 6K (gic-v3.o is around the
> same). This is arm64, I can't be bothered to rebuild for arm32, it'll be
> similar.
> 
> Given that then I really don't think it is worth introducing a two tier
> build over it.
> 
> If we really cared about these sorts of savings we would arrange to
> discard all of the unused GIC/SMMU/UART driver's .text/.data/.bss after
> boot (easy enough to achieve by putting each in a dedicated segment).
> 
> But I don't think we have enough such drivers to start worrying about
> doing that just now. We have that opportunity in our back pocket if we
> ever get to that point, which is good enough I think.
> 
> > Could you please introduce a Xen build time option in
> > xen/arch/arm/Rules.mk, called HAS_NON_STANDARD_DRIVERS, that by default
> > is n, and gate the build of gic-hip04.c on it?
> 
> Frediano, I see you've already done so in v6, thanks for that. Sorry to
> go back on it.
> 
> Assuming the rest of the series in v6 is OK (gets acked and whatever)
> then I expect I can just skip that one patch when applying and fixup the
> Makefile in the obvious way (approx s/HAS_NON.../CONFIG_ARM32/) in the
> dependent patch.

v6 is fine from my POV, you can add my Acked-by to all patches.
I am OK with dropping HAS_NON_STANDARD_DRIVERS.

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