4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Brian Gerst <[email protected]> commit 2476f2fa20568bd5d9e09cd35bcd73e99a6f4cc6 upstream 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. Signed-off-by: Brian Gerst <[email protected]> [ Changed it to do TESTB, as hpa suggested. ] Signed-off-by: Borislav Petkov <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Boris Ostrovsky <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Young <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Kristen Carlson Accardi <[email protected]> Cc: Laura Abbott <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra (Intel) <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: Ross Zwisler <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Srivatsa S. Bhat <[email protected]> Reviewed-by: Matt Helsley (VMware) <[email protected]> Reviewed-by: Alexey Makhalov <[email protected]> Reviewed-by: Bo Gan <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/cpufeature.h | 19 ++++++++++++------- arch/x86/kernel/cpu/common.c | 6 ------ 2 files changed, 12 insertions(+), 13 deletions(-) --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -132,8 +132,6 @@ extern const char * const x86_bug_flags[ */ #if defined(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 @@ -141,7 +139,7 @@ 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" @@ -166,13 +164,20 @@ static __always_inline __pure bool _stat " .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) \ --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1576,12 +1576,6 @@ 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)
