From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754563Ab0ELBG5 (ORCPT ); Tue, 11 May 2010 21:06:57 -0400 Received: from hera.kernel.org ([140.211.167.34]:46986 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752824Ab0ELBGz (ORCPT ); Tue, 11 May 2010 21:06:55 -0400 Date: Wed, 12 May 2010 01:06:41 GMT From: "tip-bot for H. Peter Anvin" Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, suresh.b.siddha@intel.com, tglx@linutronix.de, avi@redhat.com Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com, tglx@linutronix.de, avi@redhat.com In-Reply-To: <1273135546-29690-2-git-send-email-avi@redhat.com> References: <1273135546-29690-2-git-send-email-avi@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/fpu] x86: Add new static_cpu_has() function using alternatives Message-ID: Git-Commit-ID: a3c8acd04376d604370dcb6cd2143c9c14078a50 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Wed, 12 May 2010 01:06:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: a3c8acd04376d604370dcb6cd2143c9c14078a50 Gitweb: http://git.kernel.org/tip/a3c8acd04376d604370dcb6cd2143c9c14078a50 Author: H. Peter Anvin AuthorDate: Tue, 11 May 2010 17:47:07 -0700 Committer: H. Peter Anvin CommitDate: Tue, 11 May 2010 17:47:07 -0700 x86: Add new static_cpu_has() function using alternatives For CPU-feature-specific code that touches performance-critical paths, introduce a static patching version of [boot_]cpu_has(). This is run at alternatives time and is therefore not appropriate for most initialization code, but on the other hand initialization code is generally not performance critical. On gcc 4.5+ this uses the new "asm goto" feature. Signed-off-by: H. Peter Anvin Cc: Avi Kivity Cc: Suresh Siddha LKML-Reference: <1273135546-29690-2-git-send-email-avi@redhat.com> --- arch/x86/include/asm/cpufeature.h | 57 +++++++++++++++++++++++++++++++++++++ 1 files changed, 57 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 0cd82d0..9b11a5c 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -175,6 +175,7 @@ #if defined(__KERNEL__) && !defined(__ASSEMBLY__) +#include #include extern const char * const x86_cap_flags[NCAPINTS*32]; @@ -283,6 +284,62 @@ extern const char * const x86_power_flags[32]; #endif /* CONFIG_X86_64 */ +/* + * Static testing of CPU features. Used the same as boot_cpu_has(). + * These are only valid after alternatives have run, but will statically + * patch the target code for additional performance. + * + */ +static __always_inline __pure bool __static_cpu_has(u8 bit) +{ +#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5) + asm goto("1: jmp %l[t_no]\n" + "2:\n" + ".section .altinstructions,\"a\"\n" + _ASM_ALIGN "\n" + _ASM_PTR "1b\n" + _ASM_PTR "0\n" /* no replacement */ + " .byte %P0\n" /* feature bit */ + " .byte 2b - 1b\n" /* source len */ + " .byte 0\n" /* replacement len */ + " .byte 0xff + 0 - (2b-1b)\n" /* padding */ + ".previous\n" + : : "i" (bit) : : t_no); + return true; + t_no: + return false; +#else + u8 flag; + /* Open-coded due to __stringify() in ALTERNATIVE() */ + asm volatile("1: movb $0,%0\n" + "2:\n" + ".section .altinstructions,\"a\"\n" + _ASM_ALIGN "\n" + _ASM_PTR "1b\n" + _ASM_PTR "3f\n" + " .byte %P1\n" /* feature bit */ + " .byte 2b - 1b\n" /* source len */ + " .byte 4f - 3f\n" /* replacement len */ + " .byte 0xff + (4f-3f) - (2b-1b)\n" /* padding */ + ".previous\n" + ".section .altinstr_replacement,\"ax\"\n" + "3: movb $1,%0\n" + "4:\n" + ".previous\n" + : "=qm" (flag) : "i" (bit)); + return flag; +#endif +} + +#define static_cpu_has(bit) \ +( \ + __builtin_constant_p(boot_cpu_has(bit)) ? \ + boot_cpu_has(bit) : \ + (__builtin_constant_p(bit) && !((bit) & ~0xff)) ? \ + __static_cpu_has(bit) : \ + boot_cpu_has(bit) \ +) + #endif /* defined(__KERNEL__) && !defined(__ASSEMBLY__) */ #endif /* _ASM_X86_CPUFEATURE_H */