From: Brian Gerst <brge...@gmail.com> Move the code to do the dynamic check to the altinstr_aux section so that it is discarded after alternatives have run and a static branch has been chosen.
This way we're changing the dynamic branch from C code to assembly, which makes it *substantially* smaller while avoiding a completely unnecessary call to an out of line function. Boris: change it to do TESTB, as hpa suggests. Signed-off-by: Brian Gerst <brge...@gmail.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: Dave Young <dyo...@redhat.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Ingo Molnar <mi...@kernel.org> Cc: Kristen Carlson Accardi <kris...@linux.intel.com> Cc: Laura Abbott <labb...@fedoraproject.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: "Peter Zijlstra (Intel)" <pet...@infradead.org> Cc: Prarit Bhargava <pra...@redhat.com> Cc: Ross Zwisler <ross.zwis...@linux.intel.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: x86-ml <x...@kernel.org> Link: http://lkml.kernel.org/r/1452972124-7380-1-git-send-email-brge...@gmail.com Signed-off-by: Borislav Petkov <b...@suse.de> --- arch/x86/include/asm/cpufeature.h | 19 ++++++++++++------- arch/x86/kernel/cpu/common.c | 6 ------ 2 files changed, 12 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index d48bf024f335..cab88ff86caf 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -130,8 +130,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; */ #if CC_HAVE_ASM_GOTO && defined(CONFIG_X86_FAST_FEATURE_TESTS) -extern bool __static_cpu_has(u16 bit); - /* * Static testing of CPU features. Used the same as boot_cpu_has(). * These will statically patch the target code for additional @@ -139,7 +137,7 @@ extern bool __static_cpu_has(u16 bit); */ static __always_inline __pure bool _static_cpu_has(u16 bit) { - asm_volatile_goto("1: jmp %l[t_dynamic]\n" + asm_volatile_goto("1: jmp 6f\n" "2:\n" ".skip -(((5f-4f) - (2b-1b)) > 0) * " "((5f-4f) - (2b-1b)),0x90\n" @@ -164,13 +162,20 @@ static __always_inline __pure bool _static_cpu_has(u16 bit) " .byte 0\n" /* repl len */ " .byte 0\n" /* pad len */ ".previous\n" - : : "i" (bit), "i" (X86_FEATURE_ALWAYS) - : : t_dynamic, t_no); + ".section .altinstr_aux,\"ax\"\n" + "6:\n" + " testb %[bitnum],%[cap_byte]\n" + " jnz %l[t_yes]\n" + " jmp %l[t_no]\n" + ".previous\n" + : : "i" (bit), "i" (X86_FEATURE_ALWAYS), + [bitnum] "i" (1 << (bit & 7)), + [cap_byte] "m" (((const char *)boot_cpu_data.x86_capability)[bit >> 3]) + : : t_yes, t_no); + t_yes: return true; t_no: return false; - t_dynamic: - return __static_cpu_has(bit); } #define static_cpu_has(bit) \ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index ee499817f3f5..079d83fc6488 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1475,12 +1475,6 @@ void cpu_init(void) } #endif -inline bool __static_cpu_has(u16 bit) -{ - return boot_cpu_has(bit); -} -EXPORT_SYMBOL_GPL(__static_cpu_has); - static void bsp_resume(void) { if (this_cpu->c_bsp_resume) -- 2.3.5
