kernel/x86: Determine the APIC frequency in the kernel instead of the bootloader.

We use the TSC to measure the APIC frequency, but the TSC frequency
is only fully initialized in the kernel (where it's read from CPUID
on recent hardware).

Furthermore, on some more recent systems, it seems there may only be
X2APIC and no MMIO APIC timer at all, and the bootloader does not
handle that case.

The method in the kernel uses spin() instead of a fixed instruction
count as well as system_time_nsecs() and a double for (hopefully)
more accurate calibration.

At least on VMware, this method seems more accurate: the APIC frequency
read from the hypervisor CPUID leaf is 66,000,000; the old method in
in the bootloader yielded values like "65,801,075" and "65,106,382",
while the new one yields values like "65,963,920" and "65,962,580"
(those pairs of values are from two consecutive boots.)

The difference was sometimes similar (but smaller as a percentage) in
QEMU with software emulation: e.g. "993,218,085" vs. "992,965,761". But
sometimes it wasn't: e.g "991,619,585" vs. "993,689,669". (QEMU in
software mode doesn't report a frequency via hypervisor CPUID leaf.)

Change-Id: I4fb8535d1d984f13867e2f84e7dfad1ceed42c13
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8999
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

headers/private/kernel/arch/x86/apic.h

@@ -131,6 +131,7 @@ uint32		apic_lvt_error();
 void		apic_set_lvt_error(uint32 config);
 uint32		apic_lvt_initial_timer_count();
 void		apic_set_lvt_initial_timer_count(uint32 config);
+uint32		apic_lvt_current_timer_count();
 uint32		apic_lvt_timer_divide_config();
 void		apic_set_lvt_timer_divide_config(uint32 config);
 

headers/private/kernel/arch/x86/arch_kernel_args.h

@@ -29,7 +29,7 @@ typedef struct {
 	uint64	virtual_end;
 	uint64	page_hole;
 	// smp stuff
-	uint32	apic_time_cv_factor; // apic ticks per second
+	uint32	_unused; // previously: apic ticks per second
 	uint32	apic_phys;
 	FixedWidthPointer<void> apic;
 	uint32	ioapic_phys;

src/system/boot/platform/bios_ia32/smp.cpp

@@ -44,8 +44,6 @@ static struct scan_spots_struct smp_scan_spots[] = {
 	{ 0, 0, 0 }
 };
 
-extern "C" void execute_n_instructions(int count);
-
 extern "C" void smp_trampoline(void);
 extern "C" void smp_trampoline_end(void);
 
@@ -319,41 +317,6 @@ smp_do_acpi_config(void)
 }
 
 
-static void
-calculate_apic_timer_conversion_factor(void)
-{
-	int64 t1, t2;
-	uint32 config;
-	uint32 count;
-
-	// setup the timer
-	config = apic_read(APIC_LVT_TIMER);
-	config = (config & APIC_LVT_TIMER_MASK) + APIC_LVT_MASKED;
-		// timer masked, vector 0
-	apic_write(APIC_LVT_TIMER, config);
-
-	config = (apic_read(APIC_TIMER_DIVIDE_CONFIG) & ~0x0000000f);
-	apic_write(APIC_TIMER_DIVIDE_CONFIG, config | APIC_TIMER_DIVIDE_CONFIG_1);
-		// divide clock by one
-
-	t1 = system_time();
-	apic_write(APIC_INITIAL_TIMER_COUNT, 0xffffffff); // start the counter
-
-	execute_n_instructions(128 * 20000);
-
-	count = apic_read(APIC_CURRENT_TIMER_COUNT);
-	t2 = system_time();
-
-	count = 0xffffffff - count;
-
-	gKernelArgs.arch_args.apic_time_cv_factor
-		= (uint32)((1000000.0/(t2 - t1)) * count);
-
-	dprintf("APIC ticks/sec = %d\n",
-		gKernelArgs.arch_args.apic_time_cv_factor);
-}
-
-
 //	#pragma mark -
 
 
@@ -403,9 +366,6 @@ smp_init_other_cpus(void)
 
 	dprintf("smp: apic (mapped) = %p\n", (void *)gKernelArgs.arch_args.apic);
 
-	// calculate how fast the apic timer is
-	calculate_apic_timer_conversion_factor();
-
 	if (gKernelArgs.num_cpus < 2)
 		return;
 

src/system/boot/platform/bios_ia32/support.S

@@ -7,29 +7,6 @@
 #define FUNCTION(x) .global x; .type x,@function; x
 
 
-FUNCTION(execute_n_instructions):
-	movl	4(%esp), %ecx
-	shrl	$4, %ecx
-.again:
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	loop	.again
-	ret
-
 null_idt_descr:
 	.word	0
 	.word	0,0

src/system/boot/platform/efi/arch/x86/Jamfile

@@ -20,7 +20,6 @@ for platform in [ MultiBootSubDirSetup efi ] {
 			crt0-efi-$(TARGET_ARCH).S
 			entry.S
 			smp_trampoline.S
-			support.S
 			relocation_func.cpp
 			arch_mmu.cpp
 			arch_smp.cpp

src/system/boot/platform/efi/arch/x86/arch_smp.cpp

@@ -36,8 +36,6 @@
 #endif
 
 
-extern "C" void execute_n_instructions(int count);
-
 void copy_trampoline_code(uint64 trampolineCode, uint64 trampolineStack);
 void prepare_trampoline_args(uint64 trampolineCode, uint64 trampolineStack,
 	uint32 pagedir, uint64 kernelEntry, addr_t virtKernelArgs,
@@ -125,43 +123,6 @@ acpi_do_smp_config(void)
 }
 
 
-static void
-calculate_apic_timer_conversion_factor(void)
-{
-	int64 t1, t2;
-	uint32 config;
-	uint32 count;
-
-	TRACE("calculating apic timer conversion factor\n");
-
-	// setup the timer
-	config = apic_read(APIC_LVT_TIMER);
-	config = (config & APIC_LVT_TIMER_MASK) + APIC_LVT_MASKED;
-		// timer masked, vector 0
-	apic_write(APIC_LVT_TIMER, config);
-
-	config = (apic_read(APIC_TIMER_DIVIDE_CONFIG) & ~0x0000000f);
-	apic_write(APIC_TIMER_DIVIDE_CONFIG, config | APIC_TIMER_DIVIDE_CONFIG_1);
-		// divide clock by one
-
-	t1 = system_time();
-	apic_write(APIC_INITIAL_TIMER_COUNT, 0xffffffff); // start the counter
-
-	execute_n_instructions(128 * 20000);
-
-	count = apic_read(APIC_CURRENT_TIMER_COUNT);
-	t2 = system_time();
-
-	count = 0xffffffff - count;
-
-	gKernelArgs.arch_args.apic_time_cv_factor
-		= (uint32)((1000000.0/(t2 - t1)) * count);
-
-	TRACE("APIC ticks/sec = %" B_PRId32 "\n",
-		gKernelArgs.arch_args.apic_time_cv_factor);
-}
-
-
 //	#pragma mark -
 
 
@@ -211,9 +172,6 @@ arch_smp_init_other_cpus(void)
 
 	TRACE("smp: apic (mapped) = %lx\n", (addr_t)gKernelArgs.arch_args.apic.Pointer());
 
-	// calculate how fast the apic timer is
-	calculate_apic_timer_conversion_factor();
-
 	if (gKernelArgs.num_cpus < 2)
 		return;
 

src/system/boot/platform/efi/arch/x86/support.S

@@ -1,35 +0,0 @@
-/*
- * Copyright 2021-2022 Haiku, Inc. All rights reserved.
- * Released under the terms of the MIT License.
- *
- * Copyright 2001, Travis Geiselbrecht. All rights reserved.
- * Distributed under the terms of the NewOS License.
- */
-
-
-#define FUNCTION(x) .global x; .type x,@function; x
-
-
-FUNCTION(execute_n_instructions):
-	movl    4(%esp), %ecx
-	shrl    $4, %ecx
-.again:
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	xorl    %eax, %eax
-	loop	.again
-	ret
-

src/system/boot/platform/efi/arch/x86_64/Jamfile

@@ -19,7 +19,6 @@ for platform in [ MultiBootSubDirSetup efi ] {
 		crt0-efi-$(TARGET_ARCH).S
 		entry.S
 		long_smp_trampoline.S
-		support.S
 		relocation_func.cpp
 		arch_start.cpp
 		arch_smp.cpp

src/system/boot/platform/efi/arch/x86_64/support.S

@@ -1,31 +0,0 @@
-/*
-** Copyright 2001, Travis Geiselbrecht. All rights reserved.
-** Distributed under the terms of the NewOS License.
-*/
-
-
-#define FUNCTION(x) .global x; .type x,@function; x
-
-
-FUNCTION(execute_n_instructions):
-	movl	%edi, %ecx
-	shrl	$4, %ecx
-.again:
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	xorl	%eax, %eax
-	loop	.again
-	ret

src/system/kernel/arch/x86/apic.cpp

@@ -236,6 +236,16 @@ apic_set_lvt_initial_timer_count(uint32 config)
 }
 
 
+uint32
+apic_lvt_current_timer_count()
+{
+	if (sX2APIC)
+		return x86_read_msr(IA32_MSR_APIC_CURRENT_TIMER_COUNT);
+	else
+		return apic_read(APIC_CURRENT_TIMER_COUNT);
+}
+
+
 uint32
 apic_lvt_timer_divide_config()
 {

src/system/kernel/arch/x86/timers/x86_apic.cpp

@@ -1,6 +1,7 @@
 /*
+ * Copyright 2025, Haiku, Inc. All rights reserved.
  * Copyright 2008, Dustin Howett, [email protected]. All rights reserved.
- * Copyright 2002-2005, Axel Dörfler, [email protected]. All rights reserved.
+ * Copyright 2002-2010, Axel Dörfler, [email protected]. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
@@ -106,19 +107,62 @@ apic_timer_clear_hardware_timer()
 }
 
 
+//	#pragma mark - initialization
+
+
+static uint32
+calculate_apic_timer_conversion_factor()
+{
+	// setup the timer
+	uint32 config = apic_lvt_timer() & APIC_LVT_TIMER_MASK;
+	config |= APIC_LVT_MASKED;
+		// timer masked, vector 0
+	apic_set_lvt_timer(config);
+
+	config = (apic_lvt_timer_divide_config() & ~0xf);
+	apic_set_lvt_timer_divide_config(config | APIC_TIMER_DIVIDE_CONFIG_1);
+		// divide clock by one
+
+	apic_set_lvt_initial_timer_count(UINT32_MAX); // start the counter
+
+	// Use CPUID as a fence (same as in TSC calibration).
+	asm volatile ("cpuid" : : : "eax", "ebx", "ecx", "edx");
+	int64 t1 = system_time_nsecs();
+	uint32 startCount = apic_lvt_current_timer_count();
+
+	spin(5000);
+
+	asm volatile ("cpuid" : : : "eax", "ebx", "ecx", "edx");
+	int64 t2 = system_time_nsecs();
+	uint32 endCount = apic_lvt_current_timer_count();
+
+	uint32 count = startCount - endCount;
+
+	uint32 factor
+		= (uint32)(((double(1) * 1000 * 1000 * 1000) / (t2 - t1)) * count);
+
+	dprintf("APIC timer frequency: %d\n", factor);
+
+	return factor;
+}
+
+
 static status_t
 apic_timer_init(struct kernel_args *args)
 {
 	if (!apic_available())
 		return B_ERROR;
 
-	sApicTicsPerSec = args->arch_args.apic_time_cv_factor;
+	sApicTicsPerSec = calculate_apic_timer_conversion_factor();
 
 	reserve_io_interrupt_vectors(1, 0xfb - ARCH_INTERRUPT_BASE,
 		INTERRUPT_TYPE_LOCAL_IRQ);
 	install_io_interrupt_handler(0xfb - ARCH_INTERRUPT_BASE,
 		&apic_timer_interrupt, NULL, B_NO_LOCK_VECTOR);
 
+	apic_timer_per_cpu_init(args, 0);
+		// will be called on non-boot CPUs by apic_per_cpu_init()
+
 	return B_OK;
 }
 
@@ -136,5 +180,6 @@ apic_timer_per_cpu_init(struct kernel_args *args, int32 cpu)
 	config = apic_lvt_timer_divide_config() & 0xfffffff0;
 	config |= APIC_TIMER_DIVIDE_CONFIG_1; // clock division by 1
 	apic_set_lvt_timer_divide_config(config);
+
 	return B_OK;
 }