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x86/tsc: fetch frequency from CPUID when running on Xen

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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
This commit is contained in:
Roger Pau Monné 2022-03-16 09:56:40 +01:00
parent 8b1f5965d9
commit 1ca34862dc
4 changed files with 22 additions and 2 deletions
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1
sys/amd64/amd64/machdep.c
View File

@ -1167,7 +1167,6 @@ static void
native_clock_source_init(void)
{
i8254_init();
tsc_init();
}
static void

1
sys/i386/i386/machdep.c
View File

@ -208,7 +208,6 @@ static void
i386_clock_source_init(void)
{
i8254_init();
tsc_init();
}
static void

1
sys/x86/isa/clock.c
View File

@ -129,6 +129,7 @@ clock_init(void)
mtx_init(&clock_lock, "clk", NULL, MTX_SPIN | MTX_NOPROFILE);
/* Init the clock in order to use DELAY */
init_ops.early_clock_source_init();
tsc_init();
}
static int

21
sys/x86/x86/tsc.c
View File

@ -147,6 +147,21 @@ tsc_freq_vmware(void)
tsc_early_calib_exact = 1;
}
static void
tsc_freq_xen(void)
{
u_int regs[4];
/*
* Must run *after* generic tsc_freq_cpuid_vm, so that when Xen is
* emulating Viridian support the Viridian leaf is used instead.
*/
KASSERT(hv_high >= 0x40000003, ("Invalid max hypervisor leaf on Xen"));
cpuid_count(0x40000003, 0, regs);
tsc_freq = (uint64_t)(regs[2]) * 1000;
tsc_early_calib_exact = 1;
}
/*
* Calculate TSC frequency using information from the CPUID leaf 0x15 'Time
* Stamp Counter and Nominal Core Crystal Clock'. If leaf 0x15 is not
@ -358,6 +373,12 @@ probe_tsc_freq_early(void)
printf(
"Early TSC frequency %juHz derived from VMWare hypercall\n",
(uintmax_t)tsc_freq);
} else if (vm_guest == VM_GUEST_XEN) {
tsc_freq_xen();
if (bootverbose)
printf(
"Early TSC frequency %juHz derived from Xen CPUID\n",
(uintmax_t)tsc_freq);
} else if (tsc_freq_cpuid(&tsc_freq)) {
/*
* If possible, use the value obtained from CPUID as the initial