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x86 vdso gettc: eliminate duplicated code in ifunc selectors.

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Create array of rdtsc selectors and provide helper that calculate the
index into the selectors array.

Reviewed by:	gallatin, markj
MFC after:      1 week
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D27986
This commit is contained in:
Konstantin Belousov 2021-01-06 17:00:48 +02:00
parent de898cb960
commit 5bf4bafd13
1 changed files with 65 additions and 22 deletions
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87
lib/libc/x86/sys/__vdso_gettc.c
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@ -83,20 +83,6 @@ rdtsc_low_mb_none(const struct vdso_timehands *th)
return (rdtsc_low(th));
}
DEFINE_UIFUNC(static, u_int, __vdso_gettc_rdtsc_low,
(const struct vdso_timehands *th))
{
u_int p[4];
/* Not a typo, string matches our do_cpuid() registers use. */
static const char intel_id[] = "GenuntelineI";
if ((cpu_feature & CPUID_SSE2) == 0)
return (rdtsc_low_mb_none);
do_cpuid(0, p);
return (memcmp(p + 1, intel_id, sizeof(intel_id) - 1) == 0 ?
rdtsc_low_mb_lfence : rdtsc_low_mb_mfence);
}
static u_int
rdtsc32_mb_lfence(void)
{
@ -117,17 +103,74 @@ rdtsc32_mb_none(void)
return (rdtsc32());
}
DEFINE_UIFUNC(static, u_int, __vdso_gettc_rdtsc32, (void))
struct tsc_selector_tag {
u_int (*ts_rdtsc32)(void);
u_int (*ts_rdtsc_low)(const struct vdso_timehands *);
};
static const struct tsc_selector_tag tsc_selector[] = {
[0] = { /* Intel or AMD Zen+, LFENCE */
.ts_rdtsc32 = rdtsc32_mb_lfence,
.ts_rdtsc_low = rdtsc_low_mb_lfence,
},
[1] = { /* AMD, MFENCE */
.ts_rdtsc32 = rdtsc32_mb_mfence,
.ts_rdtsc_low = rdtsc_low_mb_mfence,
},
[2] = { /* No SSE2 */
.ts_rdtsc32 = rdtsc32_mb_none,
.ts_rdtsc_low = rdtsc_low_mb_none,
},
};
static int
tsc_selector_idx(u_int cpu_feature)
{
u_int p[4];
/* Not a typo, string matches our do_cpuid() registers use. */
static const char intel_id[] = "GenuntelineI";
u_int amd_feature, cpu_exthigh, cpu_id, p[4], v[3];
static const char amd_id[] = "AuthenticAMD";
static const char hygon_id[] = "HygonGenuine";
bool amd_cpu;
if (cpu_feature == 0)
return (2); /* should not happen due to RDTSC */
do_cpuid(0, p);
v[0] = p[1];
v[1] = p[3];
v[2] = p[2];
amd_cpu = memcmp(v, amd_id, sizeof(amd_id) - 1) == 0 ||
memcmp(v, hygon_id, sizeof(hygon_id) - 1) == 0;
do_cpuid(1, p);
cpu_id = p[0];
if (cpu_feature != 0) {
do_cpuid(0x80000000, p);
cpu_exthigh = p[0];
} else {
cpu_exthigh = 0;
}
if (cpu_exthigh >= 0x80000001) {
do_cpuid(0x80000001, p);
amd_feature = p[3];
} else {
amd_feature = 0;
}
if ((cpu_feature & CPUID_SSE2) == 0)
return (rdtsc32_mb_none);
do_cpuid(0, p);
return (memcmp(p + 1, intel_id, sizeof(intel_id) - 1) == 0 ?
rdtsc32_mb_lfence : rdtsc32_mb_mfence);
return (2);
return (amd_cpu ? 1 : 0);
}
DEFINE_UIFUNC(static, u_int, __vdso_gettc_rdtsc_low,
(const struct vdso_timehands *th))
{
return (tsc_selector[tsc_selector_idx(cpu_feature)].ts_rdtsc_low);
}
DEFINE_UIFUNC(static, u_int, __vdso_gettc_rdtsc32, (void))
{
return (tsc_selector[tsc_selector_idx(cpu_feature)].ts_rdtsc32);
}
#define HPET_DEV_MAP_MAX 10