arch/powerpc/kernel/setup_64.c

/*
 * 
 * Common boot and setup code.
 *
 * Copyright (C) 2001 PPC64 Team, IBM Corp
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#define DEBUG

#include <linux/export.h>
#include <linux/string.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/reboot.h>
#include <linux/delay.h>
#include <linux/initrd.h>
#include <linux/seq_file.h>
#include <linux/ioport.h>
#include <linux/console.h>
#include <linux/utsname.h>
#include <linux/tty.h>
#include <linux/root_dev.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/unistd.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
#include <linux/bootmem.h>
#include <linux/pci.h>
#include <linux/lockdep.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/nmi.h>

#include <asm/io.h>
#include <asm/kdump.h>
#include <asm/prom.h>
#include <asm/processor.h>
#include <asm/pgtable.h>
#include <asm/smp.h>
#include <asm/elf.h>
#include <asm/machdep.h>
#include <asm/paca.h>
#include <asm/time.h>
#include <asm/cputable.h>
#include <asm/dt_cpu_ftrs.h>
#include <asm/sections.h>
#include <asm/btext.h>
#include <asm/nvram.h>
#include <asm/setup.h>
#include <asm/rtas.h>
#include <asm/iommu.h>
#include <asm/serial.h>
#include <asm/cache.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/firmware.h>
#include <asm/xmon.h>
#include <asm/udbg.h>
#include <asm/kexec.h>
#include <asm/code-patching.h>
#include <asm/livepatch.h>
#include <asm/opal.h>
#include <asm/cputhreads.h>

#ifdef DEBUG
#define DBG(fmt...) udbg_printf(fmt)
#else
#define DBG(fmt...)
#endif

int spinning_secondaries;
u64 ppc64_pft_size;

struct ppc64_caches ppc64_caches = {
	.l1d = {
		.block_size = 0x40,
		.log_block_size = 6,
	},
	.l1i = {
		.block_size = 0x40,
		.log_block_size = 6
	},
};
EXPORT_SYMBOL_GPL(ppc64_caches);

#if defined(CONFIG_PPC_BOOK3E) && defined(CONFIG_SMP)
void __init setup_tlb_core_data(void)
{
	int cpu;

	BUILD_BUG_ON(offsetof(struct tlb_core_data, lock) != 0);

	for_each_possible_cpu(cpu) {
		int first = cpu_first_thread_sibling(cpu);

		/*
		 * If we boot via kdump on a non-primary thread,
		 * make sure we point at the thread that actually
		 * set up this TLB.
		 */
		if (cpu_first_thread_sibling(boot_cpuid) == first)
			first = boot_cpuid;

		paca[cpu].tcd_ptr = &paca[first].tcd;

		/*
		 * If we have threads, we need either tlbsrx.
		 * or e6500 tablewalk mode, or else TLB handlers
		 * will be racy and could produce duplicate entries.
		 * Should we panic instead?
		 */
		WARN_ONCE(smt_enabled_at_boot >= 2 &&
			  !mmu_has_feature(MMU_FTR_USE_TLBRSRV) &&
			  book3e_htw_mode != PPC_HTW_E6500,
			  "%s: unsupported MMU configuration\n", __func__);
	}
}
#endif

#ifdef CONFIG_SMP

static char *smt_enabled_cmdline;

/* Look for ibm,smt-enabled OF option */
void __init check_smt_enabled(void)
{
	struct device_node *dn;
	const char *smt_option;

	/* Default to enabling all threads */
	smt_enabled_at_boot = threads_per_core;

	/* Allow the command line to overrule the OF option */
	if (smt_enabled_cmdline) {
		if (!strcmp(smt_enabled_cmdline, "on"))
			smt_enabled_at_boot = threads_per_core;
		else if (!strcmp(smt_enabled_cmdline, "off"))
			smt_enabled_at_boot = 0;
		else {
			int smt;
			int rc;

			rc = kstrtoint(smt_enabled_cmdline, 10, &smt);
			if (!rc)
				smt_enabled_at_boot =
					min(threads_per_core, smt);
		}
	} else {
		dn = of_find_node_by_path("/options");
		if (dn) {
			smt_option = of_get_property(dn, "ibm,smt-enabled",
						     NULL);

			if (smt_option) {
				if (!strcmp(smt_option, "on"))
					smt_enabled_at_boot = threads_per_core;
				else if (!strcmp(smt_option, "off"))
					smt_enabled_at_boot = 0;
			}

			of_node_put(dn);
		}
	}
}

/* Look for smt-enabled= cmdline option */
static int __init early_smt_enabled(char *p)
{
	smt_enabled_cmdline = p;
	return 0;
}
early_param("smt-enabled", early_smt_enabled);

#endif /* CONFIG_SMP */

/** Fix up paca fields required for the boot cpu */
static void __init fixup_boot_paca(void)
{
	/* The boot cpu is started */
	get_paca()->cpu_start = 1;
	/* Allow percpu accesses to work until we setup percpu data */
	get_paca()->data_offset = 0;
}

static void __init configure_exceptions(void)
{
	/*
	 * Setup the trampolines from the lowmem exception vectors
	 * to the kdump kernel when not using a relocatable kernel.
	 */
	setup_kdump_trampoline();

	/* Under a PAPR hypervisor, we need hypercalls */
	if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
		/* Enable AIL if possible */
		pseries_enable_reloc_on_exc();

		/*
		 * Tell the hypervisor that we want our exceptions to
		 * be taken in little endian mode.
		 *
		 * We don't call this for big endian as our calling convention
		 * makes us always enter in BE, and the call may fail under
		 * some circumstances with kdump.
		 */
#ifdef __LITTLE_ENDIAN__
		pseries_little_endian_exceptions();
#endif
	} else {
		/* Set endian mode using OPAL */
		if (firmware_has_feature(FW_FEATURE_OPAL))
			opal_configure_cores();

		/* AIL on native is done in cpu_ready_for_interrupts() */
	}
}

static void cpu_ready_for_interrupts(void)
{
	/*
	 * Enable AIL if supported, and we are in hypervisor mode. This
	 * is called once for every processor.
	 *
	 * If we are not in hypervisor mode the job is done once for
	 * the whole partition in configure_exceptions().
	 */
	if (cpu_has_feature(CPU_FTR_HVMODE) &&
	    cpu_has_feature(CPU_FTR_ARCH_207S)) {
		unsigned long lpcr = mfspr(SPRN_LPCR);
		mtspr(SPRN_LPCR, lpcr | LPCR_AIL_3);
	}

	/*
	 * Fixup HFSCR:TM based on CPU features. The bit is set by our
	 * early asm init because at that point we haven't updated our
	 * CPU features from firmware and device-tree. Here we have,
	 * so let's do it.
	 */
	if (cpu_has_feature(CPU_FTR_HVMODE) && !cpu_has_feature(CPU_FTR_TM_COMP))
		mtspr(SPRN_HFSCR, mfspr(SPRN_HFSCR) & ~HFSCR_TM);

	/* Set IR and DR in PACA MSR */
	get_paca()->kernel_msr = MSR_KERNEL;
}

/*
 * Early initialization entry point. This is called by head.S
 * with MMU translation disabled. We rely on the "feature" of
 * the CPU that ignores the top 2 bits of the address in real
 * mode so we can access kernel globals normally provided we
 * only toy with things in the RMO region. From here, we do
 * some early parsing of the device-tree to setup out MEMBLOCK
 * data structures, and allocate & initialize the hash table
 * and segment tables so we can start running with translation
 * enabled.
 *
 * It is this function which will call the probe() callback of
 * the various platform types and copy the matching one to the
 * global ppc_md structure. Your platform can eventually do
 * some very early initializations from the probe() routine, but
 * this is not recommended, be very careful as, for example, the
 * device-tree is not accessible via normal means at this point.
 */

void __init early_setup(unsigned long dt_ptr)
{
	static __initdata struct paca_struct boot_paca;

	/* -------- printk is _NOT_ safe to use here ! ------- */

	/* Try new device tree based feature discovery ... */
	if (!dt_cpu_ftrs_init(__va(dt_ptr)))
		/* Otherwise use the old style CPU table */
		identify_cpu(0, mfspr(SPRN_PVR));

	/* Assume we're on cpu 0 for now. Don't write to the paca yet! */
	initialise_paca(&boot_paca, 0);
	setup_paca(&boot_paca);
	fixup_boot_paca();

	/* -------- printk is now safe to use ------- */

	/* Enable early debugging if any specified (see udbg.h) */
	udbg_early_init();

 	DBG(" -> early_setup(), dt_ptr: 0x%lx\n", dt_ptr);

	/*
	 * Do early initialization using the flattened device
	 * tree, such as retrieving the physical memory map or
	 * calculating/retrieving the hash table size.
	 */
	early_init_devtree(__va(dt_ptr));

	/* Now we know the logical id of our boot cpu, setup the paca. */
	setup_paca(&paca[boot_cpuid]);
	fixup_boot_paca();

	/*
	 * Configure exception handlers. This include setting up trampolines
	 * if needed, setting exception endian mode, etc...
	 */
	configure_exceptions();

	/* Apply all the dynamic patching */
	apply_feature_fixups();
	setup_feature_keys();

	/* Initialize the hash table or TLB handling */
	early_init_mmu();

	/*
	 * At this point, we can let interrupts switch to virtual mode
	 * (the MMU has been setup), so adjust the MSR in the PACA to
	 * have IR and DR set and enable AIL if it exists
	 */
	cpu_ready_for_interrupts();

	DBG(" <- early_setup()\n");

#ifdef CONFIG_PPC_EARLY_DEBUG_BOOTX
	/*
	 * This needs to be done *last* (after the above DBG() even)
	 *
	 * Right after we return from this function, we turn on the MMU
	 * which means the real-mode access trick that btext does will
	 * no longer work, it needs to switch to using a real MMU
	 * mapping. This call will ensure that it does
	 */
	btext_map();
#endif /* CONFIG_PPC_EARLY_DEBUG_BOOTX */
}

#ifdef CONFIG_SMP
void early_setup_secondary(void)
{
	/* Mark interrupts disabled in PACA */
	get_paca()->soft_enabled = 0;

	/* Initialize the hash table or TLB handling */
	early_init_mmu_secondary();

	/*
	 * At this point, we can let interrupts switch to virtual mode
	 * (the MMU has been setup), so adjust the MSR in the PACA to
	 * have IR and DR set.
	 */
	cpu_ready_for_interrupts();
}

#endif /* CONFIG_SMP */

#if defined(CONFIG_SMP) || defined(CONFIG_KEXEC_CORE)
static bool use_spinloop(void)
{
	if (!IS_ENABLED(CONFIG_PPC_BOOK3E))
		return true;

	/*
	 * When book3e boots from kexec, the ePAPR spin table does
	 * not get used.
	 */
	return of_property_read_bool(of_chosen, "linux,booted-from-kexec");
}

void smp_release_cpus(void)
{
	unsigned long *ptr;
	int i;

	if (!use_spinloop())
		return;

	DBG(" -> smp_release_cpus()\n");

	/* All secondary cpus are spinning on a common spinloop, release them
	 * all now so they can start to spin on their individual paca
	 * spinloops. For non SMP kernels, the secondary cpus never get out
	 * of the common spinloop.
	 */

	ptr  = (unsigned long *)((unsigned long)&__secondary_hold_spinloop
			- PHYSICAL_START);
	*ptr = ppc_function_entry(generic_secondary_smp_init);

	/* And wait a bit for them to catch up */
	for (i = 0; i < 100000; i++) {
		mb();
		HMT_low();
		if (spinning_secondaries == 0)
			break;
		udelay(1);
	}
	DBG("spinning_secondaries = %d\n", spinning_secondaries);

	DBG(" <- smp_release_cpus()\n");
}
#endif /* CONFIG_SMP || CONFIG_KEXEC_CORE */

/*
 * Initialize some remaining members of the ppc64_caches and systemcfg
 * structures
 * (at least until we get rid of them completely). This is mostly some
 * cache informations about the CPU that will be used by cache flush
 * routines and/or provided to userland
 */

static void init_cache_info(struct ppc_cache_info *info, u32 size, u32 lsize,
			    u32 bsize, u32 sets)
{
	info->size = size;
	info->sets = sets;
	info->line_size = lsize;
	info->block_size = bsize;
	info->log_block_size = __ilog2(bsize);
	if (bsize)
		info->blocks_per_page = PAGE_SIZE / bsize;
	else
		info->blocks_per_page = 0;

	if (sets == 0)
		info->assoc = 0xffff;
	else
		info->assoc = size / (sets * lsize);
}

static bool __init parse_cache_info(struct device_node *np,
				    bool icache,
				    struct ppc_cache_info *info)
{
	static const char *ipropnames[] __initdata = {
		"i-cache-size",
		"i-cache-sets",
		"i-cache-block-size",
		"i-cache-line-size",
	};
	static const char *dpropnames[] __initdata = {
		"d-cache-size",
		"d-cache-sets",
		"d-cache-block-size",
		"d-cache-line-size",
	};
	const char **propnames = icache ? ipropnames : dpropnames;
	const __be32 *sizep, *lsizep, *bsizep, *setsp;
	u32 size, lsize, bsize, sets;
	bool success = true;

	size = 0;
	sets = -1u;
	lsize = bsize = cur_cpu_spec->dcache_bsize;
	sizep = of_get_property(np, propnames[0], NULL);
	if (sizep != NULL)
		size = be32_to_cpu(*sizep);
	setsp = of_get_property(np, propnames[1], NULL);
	if (setsp != NULL)
		sets = be32_to_cpu(*setsp);
	bsizep = of_get_property(np, propnames[2], NULL);
	lsizep = of_get_property(np, propnames[3], NULL);
	if (bsizep == NULL)
		bsizep = lsizep;
	if (lsizep != NULL)
		lsize = be32_to_cpu(*lsizep);
	if (bsizep != NULL)
		bsize = be32_to_cpu(*bsizep);
	if (sizep == NULL || bsizep == NULL || lsizep == NULL)
		success = false;

	/*
	 * OF is weird .. it represents fully associative caches
	 * as "1 way" which doesn't make much sense and doesn't
	 * leave room for direct mapped. We'll assume that 0
	 * in OF means direct mapped for that reason.
	 */
	if (sets == 1)
		sets = 0;
	else if (sets == 0)
		sets = 1;

	init_cache_info(info, size, lsize, bsize, sets);

	return success;
}

void __init initialize_cache_info(void)
{
	struct device_node *cpu = NULL, *l2, *l3 = NULL;
	u32 pvr;

	DBG(" -> initialize_cache_info()\n");

	/*
	 * All shipping POWER8 machines have a firmware bug that
	 * puts incorrect information in the device-tree. This will
	 * be (hopefully) fixed for future chips but for now hard
	 * code the values if we are running on one of these
	 */
	pvr = PVR_VER(mfspr(SPRN_PVR));
	if (pvr == PVR_POWER8 || pvr == PVR_POWER8E ||
	    pvr == PVR_POWER8NVL) {
						/* size    lsize   blk  sets */
		init_cache_info(&ppc64_caches.l1i, 0x8000,   128,  128, 32);
		init_cache_info(&ppc64_caches.l1d, 0x10000,  128,  128, 64);
		init_cache_info(&ppc64_caches.l2,  0x80000,  128,  0,   512);
		init_cache_info(&ppc64_caches.l3,  0x800000, 128,  0,   8192);
	} else
		cpu = of_find_node_by_type(NULL, "cpu");

	/*
	 * We're assuming *all* of the CPUs have the same
	 * d-cache and i-cache sizes... -Peter
	 */
	if (cpu) {
		if (!parse_cache_info(cpu, false, &ppc64_caches.l1d))
			DBG("Argh, can't find dcache properties !\n");

		if (!parse_cache_info(cpu, true, &ppc64_caches.l1i))
			DBG("Argh, can't find icache properties !\n");

		/*
		 * Try to find the L2 and L3 if any. Assume they are
		 * unified and use the D-side properties.
		 */
		l2 = of_find_next_cache_node(cpu);
		of_node_put(cpu);
		if (l2) {
			parse_cache_info(l2, false, &ppc64_caches.l2);
			l3 = of_find_next_cache_node(l2);
			of_node_put(l2);
		}
		if (l3) {
			parse_cache_info(l3, false, &ppc64_caches.l3);
			of_node_put(l3);
		}
	}

	/* For use by binfmt_elf */
	dcache_bsize = ppc64_caches.l1d.block_size;
	icache_bsize = ppc64_caches.l1i.block_size;

	cur_cpu_spec->dcache_bsize = dcache_bsize;
	cur_cpu_spec->icache_bsize = icache_bsize;

	DBG(" <- initialize_cache_info()\n");
}

/* This returns the limit below which memory accesses to the linear
 * mapping are guarnateed not to cause a TLB or SLB miss. This is
 * used to allocate interrupt or emergency stacks for which our
 * exception entry path doesn't deal with being interrupted.
 */
static __init u64 safe_stack_limit(void)
{
#ifdef CONFIG_PPC_BOOK3E
	/* Freescale BookE bolts the entire linear mapping */
	if (mmu_has_feature(MMU_FTR_TYPE_FSL_E))
		return linear_map_top;
	/* Other BookE, we assume the first GB is bolted */
	return 1ul << 30;
#else
	/* BookS, the first segment is bolted */
	if (mmu_has_feature(MMU_FTR_1T_SEGMENT))
		return 1UL << SID_SHIFT_1T;
	return 1UL << SID_SHIFT;
#endif
}

void __init irqstack_early_init(void)
{
	u64 limit = safe_stack_limit();
	unsigned int i;

	/*
	 * Interrupt stacks must be in the first segment since we
	 * cannot afford to take SLB misses on them.
	 */
	for_each_possible_cpu(i) {
		softirq_ctx[i] = (struct thread_info *)
			__va(memblock_alloc_base(THREAD_SIZE,
					    THREAD_SIZE, limit));
		hardirq_ctx[i] = (struct thread_info *)
			__va(memblock_alloc_base(THREAD_SIZE,
					    THREAD_SIZE, limit));
	}
}

#ifdef CONFIG_PPC_BOOK3E
void __init exc_lvl_early_init(void)
{
	unsigned int i;
	unsigned long sp;

	for_each_possible_cpu(i) {
		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
		critirq_ctx[i] = (struct thread_info *)__va(sp);
		paca[i].crit_kstack = __va(sp + THREAD_SIZE);

		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
		dbgirq_ctx[i] = (struct thread_info *)__va(sp);
		paca[i].dbg_kstack = __va(sp + THREAD_SIZE);

		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
		mcheckirq_ctx[i] = (struct thread_info *)__va(sp);
		paca[i].mc_kstack = __va(sp + THREAD_SIZE);
	}

	if (cpu_has_feature(CPU_FTR_DEBUG_LVL_EXC))
		patch_exception(0x040, exc_debug_debug_book3e);
}
#endif

/*
 * Emergency stacks are used for a range of things, from asynchronous
 * NMIs (system reset, machine check) to synchronous, process context.
 * We set preempt_count to zero, even though that isn't necessarily correct. To
 * get the right value we'd need to copy it from the previous thread_info, but
 * doing that might fault causing more problems.
 * TODO: what to do with accounting?
 */
static void emerg_stack_init_thread_info(struct thread_info *ti, int cpu)
{
	ti->task = NULL;
	ti->cpu = cpu;
	ti->preempt_count = 0;
	ti->local_flags = 0;
	ti->flags = 0;
	klp_init_thread_info(ti);
}

/*
 * Stack space used when we detect a bad kernel stack pointer, and
 * early in SMP boots before relocation is enabled. Exclusive emergency
 * stack for machine checks.
 */
void __init emergency_stack_init(void)
{
	u64 limit;
	unsigned int i;

	/*
	 * Emergency stacks must be under 256MB, we cannot afford to take
	 * SLB misses on them. The ABI also requires them to be 128-byte
	 * aligned.
	 *
	 * Since we use these as temporary stacks during secondary CPU
	 * bringup, we need to get at them in real mode. This means they
	 * must also be within the RMO region.
	 *
	 * The IRQ stacks allocated elsewhere in this file are zeroed and
	 * initialized in kernel/irq.c. These are initialized here in order
	 * to have emergency stacks available as early as possible.
	 */
	limit = min(safe_stack_limit(), ppc64_rma_size);

	for_each_possible_cpu(i) {
		struct thread_info *ti;
		ti = __va(memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit));
		memset(ti, 0, THREAD_SIZE);
		emerg_stack_init_thread_info(ti, i);
		paca[i].emergency_sp = (void *)ti + THREAD_SIZE;

#ifdef CONFIG_PPC_BOOK3S_64
		/* emergency stack for NMI exception handling. */
		ti = __va(memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit));
		memset(ti, 0, THREAD_SIZE);
		emerg_stack_init_thread_info(ti, i);
		paca[i].nmi_emergency_sp = (void *)ti + THREAD_SIZE;

		/* emergency stack for machine check exception handling. */
		ti = __va(memblock_alloc_base(THREAD_SIZE, THREAD_SIZE, limit));
		memset(ti, 0, THREAD_SIZE);
		emerg_stack_init_thread_info(ti, i);
		paca[i].mc_emergency_sp = (void *)ti + THREAD_SIZE;
#endif
	}
}

#ifdef CONFIG_SMP
#define PCPU_DYN_SIZE		()

static void * __init pcpu_fc_alloc(unsigned int cpu, size_t size, size_t align)
{
	return __alloc_bootmem_node(NODE_DATA(early_cpu_to_node(cpu)), size, align,
				    __pa(MAX_DMA_ADDRESS));
}

static void __init pcpu_fc_free(void *ptr, size_t size)
{
	free_bootmem(__pa(ptr), size);
}

static int pcpu_cpu_distance(unsigned int from, unsigned int to)
{
	if (early_cpu_to_node(from) == early_cpu_to_node(to))
		return LOCAL_DISTANCE;
	else
		return REMOTE_DISTANCE;
}

unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
EXPORT_SYMBOL(__per_cpu_offset);

void __init setup_per_cpu_areas(void)
{
	const size_t dyn_size = PERCPU_MODULE_RESERVE + PERCPU_DYNAMIC_RESERVE;
	size_t atom_size;
	unsigned long delta;
	unsigned int cpu;
	int rc;

	/*
	 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
	 * to group units.  For larger mappings, use 1M atom which
	 * should be large enough to contain a number of units.
	 */
	if (mmu_linear_psize == MMU_PAGE_4K)
		atom_size = PAGE_SIZE;
	else
		atom_size = 1 << 20;

	rc = pcpu_embed_first_chunk(0, dyn_size, atom_size, pcpu_cpu_distance,
				    pcpu_fc_alloc, pcpu_fc_free);
	if (rc < 0)
		panic("cannot initialize percpu area (err=%d)", rc);

	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
	for_each_possible_cpu(cpu) {
                __per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
		paca[cpu].data_offset = __per_cpu_offset[cpu];
	}
}
#endif

#ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
unsigned long memory_block_size_bytes(void)
{
	if (ppc_md.memory_block_size)
		return ppc_md.memory_block_size();

	return MIN_MEMORY_BLOCK_SIZE;
}
#endif

#if defined(CONFIG_PPC_INDIRECT_PIO) || defined(CONFIG_PPC_INDIRECT_MMIO)
struct ppc_pci_io ppc_pci_io;
EXPORT_SYMBOL(ppc_pci_io);
#endif

#ifdef CONFIG_HARDLOCKUP_DETECTOR
u64 hw_nmi_get_sample_period(int watchdog_thresh)
{
	return ppc_proc_freq * watchdog_thresh;
}

/*
 * The hardlockup detector breaks PMU event based branches and is likely
 * to get false positives in KVM guests, so disable it by default.
 */
static int __init disable_hardlockup_detector(void)
{
	hardlockup_detector_disable();

	return 0;
}
early_initcall(disable_hardlockup_detector);
#endif