Date: Sat, 22 Sep 2012 12:40:52 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-9@freebsd.org Subject: svn commit: r240821 - stable/9/sys/x86/x86 Message-ID: <201209221240.q8MCeqM9067792@svn.freebsd.org>
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Author: kib Date: Sat Sep 22 12:40:52 2012 New Revision: 240821 URL: http://svn.freebsd.org/changeset/base/240821 Log: MFC r238973,r238975: Add explicit fences right before rdtsc in the timecounters 'get' functions. Modified: stable/9/sys/x86/x86/tsc.c Directory Properties: stable/9/sys/ (props changed) Modified: stable/9/sys/x86/x86/tsc.c ============================================================================== --- stable/9/sys/x86/x86/tsc.c Sat Sep 22 12:40:00 2012 (r240820) +++ stable/9/sys/x86/x86/tsc.c Sat Sep 22 12:40:52 2012 (r240821) @@ -82,7 +82,11 @@ static void tsc_freq_changed(void *arg, static void tsc_freq_changing(void *arg, const struct cf_level *level, int *status); static unsigned tsc_get_timecount(struct timecounter *tc); -static unsigned tsc_get_timecount_low(struct timecounter *tc); +static inline unsigned tsc_get_timecount_low(struct timecounter *tc); +static unsigned tsc_get_timecount_lfence(struct timecounter *tc); +static unsigned tsc_get_timecount_low_lfence(struct timecounter *tc); +static unsigned tsc_get_timecount_mfence(struct timecounter *tc); +static unsigned tsc_get_timecount_low_mfence(struct timecounter *tc); static void tsc_levels_changed(void *arg, int unit); static struct timecounter tsc_timecounter = { @@ -262,6 +266,10 @@ probe_tsc_freq(void) (vm_guest == VM_GUEST_NO && CPUID_TO_FAMILY(cpu_id) >= 0x10)) tsc_is_invariant = 1; + if (cpu_feature & CPUID_SSE2) { + tsc_timecounter.tc_get_timecount = + tsc_get_timecount_mfence; + } break; case CPU_VENDOR_INTEL: if ((amd_pminfo & AMDPM_TSC_INVARIANT) != 0 || @@ -271,6 +279,10 @@ probe_tsc_freq(void) (CPUID_TO_FAMILY(cpu_id) == 0xf && CPUID_TO_MODEL(cpu_id) >= 0x3)))) tsc_is_invariant = 1; + if (cpu_feature & CPUID_SSE2) { + tsc_timecounter.tc_get_timecount = + tsc_get_timecount_lfence; + } break; case CPU_VENDOR_CENTAUR: if (vm_guest == VM_GUEST_NO && @@ -278,6 +290,10 @@ probe_tsc_freq(void) CPUID_TO_MODEL(cpu_id) >= 0xf && (rdmsr(0x1203) & 0x100000000ULL) == 0) tsc_is_invariant = 1; + if (cpu_feature & CPUID_SSE2) { + tsc_timecounter.tc_get_timecount = + tsc_get_timecount_lfence; + } break; } @@ -328,16 +344,30 @@ init_TSC(void) #ifdef SMP -/* rmb is required here because rdtsc is not a serializing instruction. */ -#define TSC_READ(x) \ -static void \ -tsc_read_##x(void *arg) \ -{ \ - uint32_t *tsc = arg; \ - u_int cpu = PCPU_GET(cpuid); \ - \ - rmb(); \ - tsc[cpu * 3 + x] = rdtsc32(); \ +/* + * RDTSC is not a serializing instruction, and does not drain + * instruction stream, so we need to drain the stream before executing + * it. It could be fixed by use of RDTSCP, except the instruction is + * not available everywhere. + * + * Use CPUID for draining in the boot-time SMP constistency test. The + * timecounters use MFENCE for AMD CPUs, and LFENCE for others (Intel + * and VIA) when SSE2 is present, and nothing on older machines which + * also do not issue RDTSC prematurely. There, testing for SSE2 and + * vendor is too cumbersome, and we learn about TSC presence from CPUID. + * + * Do not use do_cpuid(), since we do not need CPUID results, which + * have to be written into memory with do_cpuid(). + */ +#define TSC_READ(x) \ +static void \ +tsc_read_##x(void *arg) \ +{ \ + uint32_t *tsc = arg; \ + u_int cpu = PCPU_GET(cpuid); \ + \ + __asm __volatile("cpuid" : : : "eax", "ebx", "ecx", "edx"); \ + tsc[cpu * 3 + x] = rdtsc32(); \ } TSC_READ(0) TSC_READ(1) @@ -487,7 +517,16 @@ init: for (shift = 0; shift < 31 && (tsc_freq >> shift) > max_freq; shift++) ; if (shift > 0) { - tsc_timecounter.tc_get_timecount = tsc_get_timecount_low; + if (cpu_feature & CPUID_SSE2) { + if (cpu_vendor_id == CPU_VENDOR_AMD) { + tsc_timecounter.tc_get_timecount = + tsc_get_timecount_low_mfence; + } else { + tsc_timecounter.tc_get_timecount = + tsc_get_timecount_low_lfence; + } + } else + tsc_timecounter.tc_get_timecount = tsc_get_timecount_low; tsc_timecounter.tc_name = "TSC-low"; if (bootverbose) printf("TSC timecounter discards lower %d bit(s)\n", @@ -599,16 +638,48 @@ tsc_get_timecount(struct timecounter *tc return (rdtsc32()); } -static u_int +static inline u_int tsc_get_timecount_low(struct timecounter *tc) { uint32_t rv; __asm __volatile("rdtsc; shrd %%cl, %%edx, %0" - : "=a" (rv) : "c" ((int)(intptr_t)tc->tc_priv) : "edx"); + : "=a" (rv) : "c" ((int)(intptr_t)tc->tc_priv) : "edx"); return (rv); } +static u_int +tsc_get_timecount_lfence(struct timecounter *tc __unused) +{ + + lfence(); + return (rdtsc32()); +} + +static u_int +tsc_get_timecount_low_lfence(struct timecounter *tc) +{ + + lfence(); + return (tsc_get_timecount_low(tc)); +} + +static u_int +tsc_get_timecount_mfence(struct timecounter *tc __unused) +{ + + mfence(); + return (rdtsc32()); +} + +static u_int +tsc_get_timecount_low_mfence(struct timecounter *tc) +{ + + mfence(); + return (tsc_get_timecount_low(tc)); +} + uint32_t cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th) {
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