[PATCH v6 01/51] x86/apic: Provide helpers to set local APIC timer frequency in hz and khz

[Sean Christopherson <seanjc@google.com>]

Add and use APIs to set the local APIC timer period (given a frequency)
instead of open coding the subtle HZ math in all external callers, and
make lapic_timer_period local to apic.c.  Provide APIs to specify the
frequency in both hertz and kilohertz so that Hyper-V and VMware code
aren't forced to lose precision.

Opportunistically take the frequency as a u64 to harden against the
possibility that the frequency (in Khz) is greater than 4294967, i.e. if
the APIC timer runs at ~4.29 GHz.  As pointed out by Sashiko,
4294968 * 1000 == 0x1_000002c0, and thus a Khz period of 4294968 would
silently overflow the 32-bit unsigned integer used by most callers.

Print out who set the period to maintain equivalent Hyper-V and VMware
functionality, and in general to make it easier to triage/debug issues.

Cc: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/apic.h    |  3 ++-
 arch/x86/kernel/apic/apic.c    | 19 ++++++++++++++++++-
 arch/x86/kernel/cpu/mshyperv.c |  5 +----
 arch/x86/kernel/cpu/vmware.c   |  4 +---
 arch/x86/kernel/jailhouse.c    |  2 +-
 arch/x86/kernel/tsc.c          |  2 +-
 arch/x86/kernel/tsc_msr.c      |  2 +-
 7 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 9cd493d467d4..6946220a6008 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -63,7 +63,6 @@ extern int apic_verbosity;
 extern int local_apic_timer_c2_ok;
 
 extern bool apic_is_disabled;
-extern unsigned int lapic_timer_period;
 
 extern enum apic_intr_mode_id apic_intr_mode;
 enum apic_intr_mode_id {
@@ -138,6 +137,8 @@ void register_lapic_address(unsigned long address);
 extern void setup_boot_APIC_clock(void);
 extern void setup_secondary_APIC_clock(void);
 extern void lapic_update_tsc_freq(void);
+extern void apic_set_timer_frequency_hz(u64 freq_hz, const char *source);
+extern void apic_set_timer_frequency_khz(u64 freq_khz, const char *source);
 
 #ifdef CONFIG_X86_64
 static inline bool apic_force_enable(unsigned long addr)
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 90025451ace2..9239dca91c41 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -37,6 +37,7 @@
 #include <linux/smp.h>
 #include <linux/mm.h>
 #include <linux/kvm_types.h>
+#include <linux/units.h>
 
 #include <xen/xen.h>
 
@@ -176,7 +177,7 @@ static struct resource lapic_resource = {
 };
 
 /* Measured in ticks per HZ. */
-unsigned int lapic_timer_period = 0;
+static unsigned int lapic_timer_period;
 
 static void apic_pm_activate(void);
 
@@ -796,6 +797,22 @@ bool __init apic_needs_pit(void)
 	return lapic_timer_period == 0;
 }
 
+void apic_set_timer_frequency_hz(u64 freq_hz, const char *source)
+{
+	u32 f_remainder;
+	u64 f_khz = div_u64_rem(freq_hz, HZ_PER_KHZ, &f_remainder);
+
+	lapic_timer_period = div_u64(freq_hz, HZ);
+
+	pr_info("Local APIC Timer Frequency set to %llu.%03u KHz (from '%s').\n",
+		f_khz, f_remainder, source);
+}
+
+void apic_set_timer_frequency_khz(u64 freq_khz, const char *source)
+{
+	apic_set_timer_frequency_hz(freq_khz * HZ_PER_KHZ, source);
+}
+
 static int __init calibrate_APIC_clock(void)
 {
 	struct clock_event_device *levt = this_cpu_ptr(&lapic_events);
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 185d4f677ec0..cadc7f872b4f 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -646,10 +646,7 @@ static void __init ms_hyperv_init_platform(void)
 		u64	hv_lapic_frequency;
 
 		rdmsrq(HV_X64_MSR_APIC_FREQUENCY, hv_lapic_frequency);
-		hv_lapic_frequency = div_u64(hv_lapic_frequency, HZ);
-		lapic_timer_period = hv_lapic_frequency;
-		pr_info("Hyper-V: LAPIC Timer Frequency: %#x\n",
-			lapic_timer_period);
+		apic_set_timer_frequency_hz(hv_lapic_frequency, "Hyper-V hypervisor");
 	}
 
 	register_nmi_handler(NMI_UNKNOWN, hv_nmi_unknown, NMI_FLAG_FIRST,
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 34b73573b108..22842bf5b59e 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -424,9 +424,7 @@ static void __init vmware_platform_setup(void)
 
 #ifdef CONFIG_X86_LOCAL_APIC
 		/* Skip lapic calibration since we know the bus frequency. */
-		lapic_timer_period = ecx / HZ;
-		pr_info("Host bus clock speed read from hypervisor : %u Hz\n",
-			ecx);
+		apic_set_timer_frequency_hz(ecx, "VMware hypervisor");
 #endif
 	} else {
 		pr_warn("Failed to get TSC freq from the hypervisor\n");
diff --git a/arch/x86/kernel/jailhouse.c b/arch/x86/kernel/jailhouse.c
index f58ce9220e0f..615a1f25c83a 100644
--- a/arch/x86/kernel/jailhouse.c
+++ b/arch/x86/kernel/jailhouse.c
@@ -65,7 +65,7 @@ static void jailhouse_get_wallclock(struct timespec64 *now)
 
 static void __init jailhouse_timer_init(void)
 {
-	lapic_timer_period = setup_data.v1.apic_khz * (1000 / HZ);
+	apic_set_timer_frequency_khz(setup_data.v1.apic_khz, "Jailhouse hypervisor");
 }
 
 static unsigned long jailhouse_get_tsc(void)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 723347e2cf7f..63e26805f8dd 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -717,7 +717,7 @@ unsigned long native_calibrate_tsc(void)
 	 * lapic_timer_period here to avoid having to calibrate the APIC
 	 * timer later.
 	 */
-	lapic_timer_period = crystal_khz * 1000 / HZ;
+	apic_set_timer_frequency_khz(crystal_khz, "CPUID 0x15/0x16");
 #endif
 
 	return crystal_khz * ebx_numerator / eax_denominator;
diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c
index d74743c8d2a4..4bd5f2ae656b 100644
--- a/arch/x86/kernel/tsc_msr.c
+++ b/arch/x86/kernel/tsc_msr.c
@@ -212,7 +212,7 @@ unsigned long cpu_khz_from_msr(void)
 		pr_err("Error MSR_FSB_FREQ index %d is unknown\n", index);
 
 #ifdef CONFIG_X86_LOCAL_APIC
-	lapic_timer_period = (freq * 1000) / HZ;
+	apic_set_timer_frequency_khz(freq, "MSR_FSB_FREQ");
 #endif
 
 	/*
-- 
2.55.0.679.g6767b8d81c-goog