From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760153AbYACAvx (ORCPT ); Wed, 2 Jan 2008 19:51:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758219AbYACAuG (ORCPT ); Wed, 2 Jan 2008 19:50:06 -0500 Received: from ns2.suse.de ([195.135.220.15]:58342 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755199AbYACAuC (ORCPT ); Wed, 2 Jan 2008 19:50:02 -0500 From: Andi Kleen References: <20080103149.088038000@suse.de> In-Reply-To: <20080103149.088038000@suse.de> To: linux-kernel@vger.kernel.org Subject: [PATCH] [6/20] x86: Remove get_cycles_sync Message-Id: <20080103005001.72C6314D40@wotan.suse.de> Date: Thu, 3 Jan 2008 01:50:01 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org And replace with nsec_barrier() as needed which has the same effect of preventing unnecessary speculation around RDTSC. For the standard gtod() like calls the previous patch already added the necessary barriers Signed-off-by: Andi Kleen --- arch/x86/kernel/time_64.c | 4 +++- arch/x86/kernel/tsc_64.c | 17 +++++++++++------ arch/x86/kernel/tsc_sync.c | 6 ++++-- include/asm-x86/tsc.h | 44 ++++---------------------------------------- 4 files changed, 22 insertions(+), 49 deletions(-) Index: linux/arch/x86/kernel/time_64.c =================================================================== --- linux.orig/arch/x86/kernel/time_64.c +++ linux/arch/x86/kernel/time_64.c @@ -81,9 +81,11 @@ unsigned long __init native_calculate_cp wrmsrl(MSR_K7_PERFCTR0 + i, 0); wrmsrl(MSR_K7_EVNTSEL0 + i, 1 << 22 | 3 << 16 | 0x76); rdtscl(tsc_start); + nsec_barrier(); do { rdmsrl(MSR_K7_PERFCTR0 + i, pmc_now); - tsc_now = get_cycles_sync(); + nsec_barrier(); + tsc_now = get_cycles(); } while ((tsc_now - tsc_start) < TICK_COUNT); local_irq_restore(flags); Index: linux/arch/x86/kernel/tsc_64.c =================================================================== --- linux.orig/arch/x86/kernel/tsc_64.c +++ linux/arch/x86/kernel/tsc_64.c @@ -181,12 +181,14 @@ static unsigned long __init tsc_read_ref int i; for (i = 0; i < MAX_RETRIES; i++) { - t1 = get_cycles_sync(); + nsec_barrier(); + t1 = get_cycles(); if (hpet) *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; else *pm = acpi_pm_read_early(); - t2 = get_cycles_sync(); + nsec_barrier(); + t2 = get_cycles(); if ((t2 - t1) < SMI_TRESHOLD) return t2; } @@ -210,9 +212,11 @@ void __init tsc_calibrate(void) outb(0xb0, 0x43); outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); - tr1 = get_cycles_sync(); + tr1 = get_cycles(); + nsec_barrier(); while ((inb(0x61) & 0x20) == 0); - tr2 = get_cycles_sync(); + nsec_barrier(); + tr2 = get_cycles(); tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); @@ -298,15 +302,16 @@ __setup("notsc", notsc_setup); /* clock source code: */ +/* Caller must do nsec_barrier()s */ static cycle_t read_tsc(void) { - cycle_t ret = (cycle_t)get_cycles_sync(); + cycle_t ret = (cycle_t)get_cycles(); return ret; } static cycle_t __vsyscall_fn vread_tsc(void) { - cycle_t ret = (cycle_t)vget_cycles_sync(); + cycle_t ret = (cycle_t)vget_cycles(); return ret; } Index: linux/include/asm-x86/tsc.h =================================================================== --- linux.orig/include/asm-x86/tsc.h +++ linux/include/asm-x86/tsc.h @@ -36,61 +36,25 @@ static inline cycles_t get_cycles(void) return ret; } -/* Like get_cycles, but make sure the CPU is synchronized. */ -static __always_inline cycles_t __get_cycles_sync(void) -{ - unsigned long long ret; - unsigned eax, edx; - - /* - * Use RDTSCP if possible; it is guaranteed to be synchronous - * and doesn't cause a VMEXIT on Hypervisors - */ - alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP, - ASM_OUTPUT2("=a" (eax), "=d" (edx)), - "a" (0U), "d" (0U) : "ecx", "memory"); - ret = (((unsigned long long)edx) << 32) | ((unsigned long long)eax); - if (ret) - return ret; - - /* - * Don't do an additional sync on CPUs where we know - * RDTSC is already synchronous: - */ - alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC, - "=a" (eax), "0" (1) : "ebx","ecx","edx","memory"); - - return 0; -} - -static __always_inline cycles_t get_cycles_sync(void) -{ - unsigned long long ret; - ret = __get_cycles_sync(); - if (!ret) - rdtscll(ret); - return ret; -} - #ifdef CONFIG_PARAVIRT /* * For paravirt guests, some functionalities are executed through function * pointers in the various pvops structures. * These function pointers exist inside the kernel and can not * be accessed by user space. To avoid this, we make a copy of the - * get_cycles_sync (called in kernel) but force the use of native_read_tsc. + * get_cycles (called in kernel) but force the use of native_read_tsc. * Ideally, the guest should set up it's own clock and vread */ -static __always_inline long long vget_cycles_sync(void) +static __always_inline long long vget_cycles(void) { unsigned long long ret; - ret = __get_cycles_sync(); + ret = get_cycles(); if (!ret) ret = native_read_tsc(); return ret; } #else -# define vget_cycles_sync() get_cycles_sync() +# define vget_cycles() get_cycles() #endif extern void tsc_init(void); Index: linux/arch/x86/kernel/tsc_sync.c =================================================================== --- linux.orig/arch/x86/kernel/tsc_sync.c +++ linux/arch/x86/kernel/tsc_sync.c @@ -46,7 +46,8 @@ static __cpuinit void check_tsc_warp(voi cycles_t start, now, prev, end; int i; - start = get_cycles_sync(); + start = get_cycles(); + nsec_barrier(); /* * The measurement runs for 20 msecs: */ @@ -61,7 +62,8 @@ static __cpuinit void check_tsc_warp(voi */ __raw_spin_lock(&sync_lock); prev = last_tsc; - now = get_cycles_sync(); + nsec_barrier(); + now = get_cycles(); last_tsc = now; __raw_spin_unlock(&sync_lock);