WSL2-Linux-Kernel/arch/x86/hyperv/hv_apic.c

// SPDX-License-Identifier: GPL-2.0

/*
 * Hyper-V specific APIC code.
 *
 * Copyright (C) 2018, Microsoft, Inc.
 *
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 * NON INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 */

#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/clockchips.h>
#include <linux/hyperv.h>
#include <linux/slab.h>
#include <linux/cpuhotplug.h>
#include <asm/hypervisor.h>
#include <asm/mshyperv.h>
#include <asm/apic.h>

#include <asm/trace/hyperv.h>

static struct apic orig_apic;

static u64 hv_apic_icr_read(void)
{
	u64 reg_val;

	rdmsrl(HV_X64_MSR_ICR, reg_val);
	return reg_val;
}

static void hv_apic_icr_write(u32 low, u32 id)
{
	u64 reg_val;

	reg_val = SET_XAPIC_DEST_FIELD(id);
	reg_val = reg_val << 32;
	reg_val |= low;

	wrmsrl(HV_X64_MSR_ICR, reg_val);
}

static u32 hv_apic_read(u32 reg)
{
	u32 reg_val, hi;

	switch (reg) {
	case APIC_EOI:
		rdmsr(HV_X64_MSR_EOI, reg_val, hi);
		(void)hi;
		return reg_val;
	case APIC_TASKPRI:
		rdmsr(HV_X64_MSR_TPR, reg_val, hi);
		(void)hi;
		return reg_val;

	default:
		return native_apic_mem_read(reg);
	}
}

static void hv_apic_write(u32 reg, u32 val)
{
	switch (reg) {
	case APIC_EOI:
		wrmsr(HV_X64_MSR_EOI, val, 0);
		break;
	case APIC_TASKPRI:
		wrmsr(HV_X64_MSR_TPR, val, 0);
		break;
	default:
		native_apic_mem_write(reg, val);
	}
}

static void hv_apic_eoi_write(u32 reg, u32 val)
{
	struct hv_vp_assist_page *hvp = hv_vp_assist_page[smp_processor_id()];

	if (hvp && (xchg(&hvp->apic_assist, 0) & 0x1))
		return;

	wrmsr(HV_X64_MSR_EOI, val, 0);
}

static bool cpu_is_self(int cpu)
{
	return cpu == smp_processor_id();
}

/*
 * IPI implementation on Hyper-V.
 */
static bool __send_ipi_mask_ex(const struct cpumask *mask, int vector,
		bool exclude_self)
{
	struct hv_send_ipi_ex **arg;
	struct hv_send_ipi_ex *ipi_arg;
	unsigned long flags;
	int nr_bank = 0;
	u64 status = HV_STATUS_INVALID_PARAMETER;

	if (!(ms_hyperv.hints & HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED))
		return false;

	local_irq_save(flags);
	arg = (struct hv_send_ipi_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);

	ipi_arg = *arg;
	if (unlikely(!ipi_arg))
		goto ipi_mask_ex_done;

	ipi_arg->vector = vector;
	ipi_arg->reserved = 0;
	ipi_arg->vp_set.valid_bank_mask = 0;

	/*
	 * Use HV_GENERIC_SET_ALL and avoid converting cpumask to VP_SET
	 * when the IPI is sent to all currently present CPUs.
	 */
	if (!cpumask_equal(mask, cpu_present_mask) || exclude_self) {
		ipi_arg->vp_set.format = HV_GENERIC_SET_SPARSE_4K;

		nr_bank = cpumask_to_vpset_skip(&(ipi_arg->vp_set), mask,
				exclude_self ? cpu_is_self : NULL);

		/*
		 * 'nr_bank <= 0' means some CPUs in cpumask can't be
		 * represented in VP_SET. Return an error and fall back to
		 * native (architectural) method of sending IPIs.
		 */
		if (nr_bank <= 0)
			goto ipi_mask_ex_done;
	} else {
		ipi_arg->vp_set.format = HV_GENERIC_SET_ALL;
	}

	status = hv_do_rep_hypercall(HVCALL_SEND_IPI_EX, 0, nr_bank,
			      ipi_arg, NULL);

ipi_mask_ex_done:
	local_irq_restore(flags);
	return hv_result_success(status);
}

static bool __send_ipi_mask(const struct cpumask *mask, int vector,
		bool exclude_self)
{
	int cur_cpu, vcpu, this_cpu = smp_processor_id();
	struct hv_send_ipi ipi_arg;
	u64 status;
	unsigned int weight;

	trace_hyperv_send_ipi_mask(mask, vector);

	weight = cpumask_weight(mask);

	/*
	 * Do nothing if
	 *   1. the mask is empty
	 *   2. the mask only contains self when exclude_self is true
	 */
	if (weight == 0 ||
	    (exclude_self && weight == 1 && cpumask_test_cpu(this_cpu, mask)))
		return true;

	if (!hv_hypercall_pg)
		return false;

	if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
		return false;

	/*
	 * From the supplied CPU set we need to figure out if we can get away
	 * with cheaper HVCALL_SEND_IPI hypercall. This is possible when the
	 * highest VP number in the set is < 64. As VP numbers are usually in
	 * ascending order and match Linux CPU ids, here is an optimization:
	 * we check the VP number for the highest bit in the supplied set first
	 * so we can quickly find out if using HVCALL_SEND_IPI_EX hypercall is
	 * a must. We will also check all VP numbers when walking the supplied
	 * CPU set to remain correct in all cases.
	 */
	if (hv_cpu_number_to_vp_number(cpumask_last(mask)) >= 64)
		goto do_ex_hypercall;

	ipi_arg.vector = vector;
	ipi_arg.cpu_mask = 0;

	for_each_cpu(cur_cpu, mask) {
		if (exclude_self && cur_cpu == this_cpu)
			continue;
		vcpu = hv_cpu_number_to_vp_number(cur_cpu);
		if (vcpu == VP_INVAL)
			return false;

		/*
		 * This particular version of the IPI hypercall can
		 * only target upto 64 CPUs.
		 */
		if (vcpu >= 64)
			goto do_ex_hypercall;

		__set_bit(vcpu, (unsigned long *)&ipi_arg.cpu_mask);
	}

	status = hv_do_fast_hypercall16(HVCALL_SEND_IPI, ipi_arg.vector,
				     ipi_arg.cpu_mask);
	return hv_result_success(status);

do_ex_hypercall:
	return __send_ipi_mask_ex(mask, vector, exclude_self);
}

static bool __send_ipi_one(int cpu, int vector)
{
	int vp = hv_cpu_number_to_vp_number(cpu);
	u64 status;

	trace_hyperv_send_ipi_one(cpu, vector);

	if (!hv_hypercall_pg || (vp == VP_INVAL))
		return false;

	if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
		return false;

	if (vp >= 64)
		return __send_ipi_mask_ex(cpumask_of(cpu), vector, false);

	status = hv_do_fast_hypercall16(HVCALL_SEND_IPI, vector, BIT_ULL(vp));
	return hv_result_success(status);
}

static void hv_send_ipi(int cpu, int vector)
{
	if (!__send_ipi_one(cpu, vector))
		orig_apic.send_IPI(cpu, vector);
}

static void hv_send_ipi_mask(const struct cpumask *mask, int vector)
{
	if (!__send_ipi_mask(mask, vector, false))
		orig_apic.send_IPI_mask(mask, vector);
}

static void hv_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
{
	if (!__send_ipi_mask(mask, vector, true))
		orig_apic.send_IPI_mask_allbutself(mask, vector);
}

static void hv_send_ipi_allbutself(int vector)
{
	hv_send_ipi_mask_allbutself(cpu_online_mask, vector);
}

static void hv_send_ipi_all(int vector)
{
	if (!__send_ipi_mask(cpu_online_mask, vector, false))
		orig_apic.send_IPI_all(vector);
}

static void hv_send_ipi_self(int vector)
{
	if (!__send_ipi_one(smp_processor_id(), vector))
		orig_apic.send_IPI_self(vector);
}

void __init hv_apic_init(void)
{
	if (ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) {
		pr_info("Hyper-V: Using IPI hypercalls\n");
		/*
		 * Set the IPI entry points.
		 */
		orig_apic = *apic;

		apic->send_IPI = hv_send_ipi;
		apic->send_IPI_mask = hv_send_ipi_mask;
		apic->send_IPI_mask_allbutself = hv_send_ipi_mask_allbutself;
		apic->send_IPI_allbutself = hv_send_ipi_allbutself;
		apic->send_IPI_all = hv_send_ipi_all;
		apic->send_IPI_self = hv_send_ipi_self;
	}

	if (ms_hyperv.hints & HV_X64_APIC_ACCESS_RECOMMENDED) {
		pr_info("Hyper-V: Using enlightened APIC (%s mode)",
			x2apic_enabled() ? "x2apic" : "xapic");
		/*
		 * When in x2apic mode, don't use the Hyper-V specific APIC
		 * accessors since the field layout in the ICR register is
		 * different in x2apic mode. Furthermore, the architectural
		 * x2apic MSRs function just as well as the Hyper-V
		 * synthetic APIC MSRs, so there's no benefit in having
		 * separate Hyper-V accessors for x2apic mode. The only
		 * exception is hv_apic_eoi_write, because it benefits from
		 * lazy EOI when available, but the same accessor works for
		 * both xapic and x2apic because the field layout is the same.
		 */
		apic_set_eoi_write(hv_apic_eoi_write);
		if (!x2apic_enabled()) {
			apic->read      = hv_apic_read;
			apic->write     = hv_apic_write;
			apic->icr_write = hv_apic_icr_write;
			apic->icr_read  = hv_apic_icr_read;
		}
	}
}