Messages in this thread | | | Date | Tue, 24 Nov 2015 14:05:10 +0100 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH 3/3] x86/cpufeature: Remove unused and seldomly used cpu_has_xx macros |
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On Tue, Nov 10, 2015 at 12:48:42PM +0100, Borislav Petkov wrote: > From: Borislav Petkov <bp@suse.de> > > Those are stupid and code should use static_cpu_has_safe() anyway. Kill > the least used and unused ones. > > Signed-off-by: Borislav Petkov <bp@suse.de> > Cc: Herbert Xu <herbert@gondor.apana.org.au> > Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> > Cc: Matt Mackall <mpm@selenic.com> > Cc: Chris Mason <clm@fb.com> > Cc: Josef Bacik <jbacik@fb.com> > Cc: David Sterba <dsterba@suse.com> > --- > arch/x86/crypto/chacha20_glue.c | 2 +- > arch/x86/crypto/crc32c-intel_glue.c | 3 ++- > arch/x86/include/asm/cmpxchg_32.h | 2 +- > arch/x86/include/asm/cpufeature.h | 32 +++-------------------------- > arch/x86/include/asm/smp.h | 2 +- > arch/x86/kernel/cpu/amd.c | 2 +- > arch/x86/kernel/cpu/intel.c | 3 ++- > arch/x86/kernel/cpu/mtrr/generic.c | 2 +- > arch/x86/kernel/cpu/mtrr/main.c | 2 +- > arch/x86/kernel/cpu/perf_event_amd.c | 4 ++-- > arch/x86/kernel/cpu/perf_event_amd_uncore.c | 8 ++++---- > arch/x86/kernel/fpu/init.c | 4 ++-- > arch/x86/kernel/hw_breakpoint.c | 3 ++- > arch/x86/kernel/vm86_32.c | 4 +++- > arch/x86/mm/setup_nx.c | 4 ++-- > drivers/char/hw_random/via-rng.c | 5 +++-- > drivers/crypto/padlock-aes.c | 2 +- > drivers/crypto/padlock-sha.c | 3 ++- > fs/btrfs/disk-io.c | 2 +- > 19 files changed, 35 insertions(+), 54 deletions(-)
Ok, 0day says this patch makes tiny not so tiny:
i386-tinyconfig vmlinux size:
+-------+------+-------+-----+--------------------------------------------------------------------------------------+ | TOTAL | TEXT | DATA | BSS | | +-------+------+-------+-----+--------------------------------------------------------------------------------------+ | +4646 | +64 | +4096 | 0 | ab9976b5af96 x86/cpufeature: Remove unused and seldomly used cpu_has_xx macros | | -32 | -32 | 0 | 0 | 13e835020a02 x86/cpufeature: Cleanup get_cpu_cap() | | +32 | +32 | 0 | 0 | 3615f94f0486 x86/cpufeature: Move some of the scattered feature bits to x86_capabili | | +136 | +32 | 0 | 0 | 506d983184f4 Merge branch 'tip-fpu-xsave' into rc2+ | | +4782 | +96 | +4096 | 0 | ALL COMMITS | +-------+------+-------+-----+--------------------------------------------------------------------------------------+
Btw, thanks 0day!
The problem comes from static_cpu_has_safe() adding the alternatives and fallback machinery. For example, before the patch, we had this at the cpu_has_* testing sites:
movl boot_cpu_data+20, %eax # MEM[(const long unsigned int *)&boot_cpu_data + 20B], D.19113 testl $2097152, %eax #, D.19113 je .L166 #,
and now we get this:
#APP # 449 "arch/x86/kernel/cpu/intel.c" 1 # 0 "" 2 # 511 "./arch/x86/include/asm/cpufeature.h" 1 1: jmp .L166 # 2: .skip -(((5f-4f) - (2b-1b)) > 0) * ((5f-4f) - (2b-1b)),0x90 3: .section .altinstructions,"a" .long 1b - . .long 4f - . .word 117 # .byte 3b - 1b .byte 5f - 4f .byte 3b - 2b .previous .section .altinstr_replacement,"ax" 4: jmp .L167 # 5: .previous .section .altinstructions,"a" .long 1b - . .long 0 .word 21 # .byte 3b - 1b .byte 0 .byte 0 .previous
# 0 "" 2 #NO_APP jmp .L168 # .L166: movl $21, %eax #, call __static_cpu_has_safe # testb %al, %al # D.19126 je .L167 #, .L168: #APP # 453 "arch/x86/kernel/cpu/intel.c" 1 # 0 "" 2 #NO_APP
That gets spread among .altinstructions, .altinstr_replacement, .text etc sections. .data grows too probably because of the NOP padding :-\
text data bss dec hex filename before: 644896 127436 1189384 1961716 1deef4 vmlinux after: 645446 131532 1189384 1966362 1e011a vmlinux
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al before: [12] .altinstructions PROGBITS c10bdf48 0bef48 000680 00 A 0 0 1 after: [12] .altinstructions PROGBITS c10bff48 0c0f48 0007d2 00 A 0 0 1
before: [13] .altinstr_replace PROGBITS c10be5c8 0bf5c8 00016c 00 AX 0 0 1 after: [13] .altinstr_replace PROGBITS c10c071a 0c171a 0001ad 00 AX 0 0 1
before: [ 7] .data PROGBITS c1092000 093000 0132a0 00 WA 0 0 4096 after: [ 7] .data PROGBITS c1093000 094000 0142a0 00 WA 0 0 4096
So I'm wondering if we should make a config option which converts static_cpu_has* macros to boot_cpu_has()? That should slim down the kernel even more but it won't benefit from the speedup of the static_cpu_has* stuff.
Josh, thoughts?
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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