x86/tsc: fetch frequency from CPUID when running on Xen
Introduce a helper to fetch the TSC frequency from CPUID when running under Xen. Since the TSC can also be initialized early when running as a Xen guest pull out the call to tsc_init() from the early_clock_source_init() handlers and place it in clock_init(), as otherwise all handlers would call tsc_init() anyway. Reviewed by: markj Sponsored by: Citrix Systems R&D Differential revision: https://reviews.freebsd.org/D34581
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@ -1167,7 +1167,6 @@ static void
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native_clock_source_init(void)
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{
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i8254_init();
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tsc_init();
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}
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static void
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@ -208,7 +208,6 @@ static void
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i386_clock_source_init(void)
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{
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i8254_init();
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tsc_init();
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}
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static void
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@ -129,6 +129,7 @@ clock_init(void)
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mtx_init(&clock_lock, "clk", NULL, MTX_SPIN | MTX_NOPROFILE);
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/* Init the clock in order to use DELAY */
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init_ops.early_clock_source_init();
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tsc_init();
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}
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static int
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@ -147,6 +147,21 @@ tsc_freq_vmware(void)
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tsc_early_calib_exact = 1;
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}
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static void
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tsc_freq_xen(void)
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{
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u_int regs[4];
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/*
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* Must run *after* generic tsc_freq_cpuid_vm, so that when Xen is
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* emulating Viridian support the Viridian leaf is used instead.
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*/
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KASSERT(hv_high >= 0x40000003, ("Invalid max hypervisor leaf on Xen"));
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cpuid_count(0x40000003, 0, regs);
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tsc_freq = (uint64_t)(regs[2]) * 1000;
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tsc_early_calib_exact = 1;
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}
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/*
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* Calculate TSC frequency using information from the CPUID leaf 0x15 'Time
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* Stamp Counter and Nominal Core Crystal Clock'. If leaf 0x15 is not
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@ -358,6 +373,12 @@ probe_tsc_freq_early(void)
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printf(
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"Early TSC frequency %juHz derived from VMWare hypercall\n",
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(uintmax_t)tsc_freq);
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} else if (vm_guest == VM_GUEST_XEN) {
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tsc_freq_xen();
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if (bootverbose)
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printf(
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"Early TSC frequency %juHz derived from Xen CPUID\n",
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(uintmax_t)tsc_freq);
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} else if (tsc_freq_cpuid(&tsc_freq)) {
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/*
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* If possible, use the value obtained from CPUID as the initial
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