I don't know if this is already known (I don't see a pullup request for =20
it), but cross compiling a 3.0_BETA release from i386 fails like this:

#   compile  procfs//usr/src/sys/lkm/vfs/miscfs/procfs/procfs_machdep.o
/usr/build/obj64/tooldir.NetBSD-3.0_BETA-i386/bin/x86_64--netbsd-gcc -=20
O2 -ffreestanding  -mcmodel=3Dkernel -Wall -Wstrict-prototypes -Wmissing-=20
prototypes -Wpointer-arith -Wno-sign-compare -Wno-traditional -Wno-=20
uninitialized  -Werror   -nostdinc -I. -I/usr/src/sys/lkm/vfs/miscfs/=20
procfs -isystem /usr/src/sys -isystem /usr/src/sys/arch -D_KERNEL -=20
D_LKM  -c    /usr/src/sys/arch/i386/i386/procfs_machdep.c
/usr/src/sys/arch/i386/i386/procfs_machdep.c: In function =20
`procfs_getonecpu':
/usr/src/sys/arch/i386/i386/procfs_machdep.c:135: error: structure has =20
no member named `ci_vendor'
/usr/src/sys/arch/i386/i386/procfs_machdep.c:136: error: structure has =20
no member named `ci_cpuid_level'
/usr/src/sys/arch/i386/i386/procfs_machdep.c:137: error: `cpu_class' =20
undeclared (first use in this function)
/usr/src/sys/arch/i386/i386/procfs_machdep.c:137: error: (Each =20
undeclared identifier is reported only once
/usr/src/sys/arch/i386/i386/procfs_machdep.c:137: error: for each =20
function it appears in.)
/usr/src/sys/arch/i386/i386/procfs_machdep.c:138: error: structure has =20
no member named `ci_cpuid_level'
/usr/src/sys/arch/i386/i386/procfs_machdep.c:148: error: structure has =20
no member named `ci_cpuid_level'
/usr/src/sys/arch/i386/i386/procfs_machdep.c:165: warning: long long =20
int format, u_int64_t arg (arg 4)
/usr/src/sys/arch/i386/i386/procfs_machdep.c:165: warning: long long =20
int format, u_int64_t arg (arg 5)
/usr/src/sys/arch/i386/i386/procfs_machdep.c:184: error: structure has =20
no member named `ci_cpuid_level'

*** Failed target:  procfs_machdep.o
*** Failed command: /usr/build/obj64/tooldir.NetBSD-3.0_BETA-i386/bin/=20
x86_64--netbsd-gcc -O2 -ffreestanding -mcmodel=3Dkernel -Wall -Wstrict-=20
prototypes -Wmissing-prototypes -Wpointer-arith -Wno-sign-compare -Wno-=20
traditional -Wno-uninitialized -Werror -nostdinc -I. -I/usr/src/sys/=20
lkm/vfs/miscfs/procfs -isystem /usr/src/sys -isystem /usr/src/sys/arch =20
-D_KERNEL -D_LKM -c /usr/src/sys/arch/i386/i386/procfs_machdep.c
*** Error code 1

Stop.
nbmake: stopped in /usr/src/sys/lkm/vfs/miscfs/procfs

Kind regards,
dieter