Re: [kbuild-all] [tip:x86/cpu 8/12] arch/x86/kernel/cpu/intel_rdt.c:63: error: unknown field 'cache' specified in initializer

[Fengguang Wu]

On Sat, Apr 15, 2017 at 07:40:34AM +0200, Thomas Gleixner wrote:
> On Sat, 15 Apr 2017, kbuild test robot wrote:
>
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/cpu
> > head:   64e8ed3d4a6dcd6139a869a3e760e625cb0d3022
> > commit: 05b93417ce5b924c6652de19fdcc27439ab37c90 [8/12] x86/intel_rdt/mba: Add primary support for Memory Bandwidth Allocation (MBA)
> > config: x86_64-randconfig-s0-04150438 (attached as .config)
> > compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
> > reproduce:
> >         git checkout 05b93417ce5b924c6652de19fdcc27439ab37c90
> >         # save the attached .config to linux build tree
> >         make ARCH=x86_64
>
> That's weird.
>
> > c1c7c3f9 Fenghua Yu      2016-10-22  57  	{
> > c1c7c3f9 Fenghua Yu      2016-10-22  58  		.name			= "L3",
> > c1c7c3f9 Fenghua Yu      2016-10-22  59  		.domains		= domain_init(RDT_RESOURCE_L3),
> > c1c7c3f9 Fenghua Yu      2016-10-22  60  		.msr_base		= IA32_L3_CBM_BASE,
> > 0921c547 Thomas Gleixner 2017-04-14  61  		.msr_update		= cat_wrmsr,
> > c1c7c3f9 Fenghua Yu      2016-10-22  62  		.cache_level		= 3,
> > d3e11b4d Thomas Gleixner 2017-04-14 @63  		.cache = {
> > d3e11b4d Thomas Gleixner 2017-04-14 @64  			.min_cbm_bits	= 1,
> > d3e11b4d Thomas Gleixner 2017-04-14 @65  			.cbm_idx_mult	= 1,
> > d3e11b4d Thomas Gleixner 2017-04-14  66  			.cbm_idx_offset	= 0,
> > d3e11b4d Thomas Gleixner 2017-04-14  67  		},
> > c1c7c3f9 Fenghua Yu      2016-10-22  68  	},
> >
> > :::::: The code at line 63 was first introduced by commit
> > :::::: d3e11b4d6ffd363747ac6e6b5522baa9ca5a20c0 x86/intel_rdt: Move CBM specific data into a struct
>
> So the compiler fails to handle the anon union, which was introduced in
> 05b93417ce5b924. No idea why, but that concept is not new and widely used
> in the kernel already.

It looks like a problem with gcc 4.4:

       Bug 42875 - gcc disallows named initializers for anonymous unions
       https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42875
       https://gcc.gnu.org/bugzilla/show_bug.cgi?id=10676

       gcc-4.4.3 lets you statically initialize named fields, and
       lets you assign to anonymous union members, but you cannot
       statically initialize a named member of an anonymous union.

Thanks,
Fengguang