1 files changed, 470 insertions, 0 deletions
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
new file mode 100644
index 000000000..e97bab7b0
--- /dev/null
+++ b/arch/x86/xen/smp_pv.c
@@ -0,0 +1,470 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xen SMP support
+ *
+ * This file implements the Xen versions of smp_ops.  SMP under Xen is
+ * very straightforward.  Bringing a CPU up is simply a matter of
+ * loading its initial context and setting it running.
+ *
+ * IPIs are handled through the Xen event mechanism.
+ *
+ * Because virtual CPUs can be scheduled onto any real CPU, there's no
+ * useful topology information for the kernel to make use of.  As a
+ * result, all CPUs are treated as if they're single-core and
+ * single-threaded.
+ */
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/irq_work.h>
+#include <linux/tick.h>
+#include <linux/nmi.h>
+#include <linux/cpuhotplug.h>
+#include <linux/stackprotector.h>
+#include <linux/pgtable.h>
+
+#include <asm/paravirt.h>
+#include <asm/idtentry.h>
+#include <asm/desc.h>
+#include <asm/cpu.h>
+#include <asm/io_apic.h>
+
+#include <xen/interface/xen.h>
+#include <xen/interface/vcpu.h>
+#include <xen/interface/xenpmu.h>
+
+#include <asm/spec-ctrl.h>
+#include <asm/xen/interface.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/xen.h>
+#include <xen/page.h>
+#include <xen/events.h>
+
+#include <xen/hvc-console.h>
+#include "xen-ops.h"
+#include "mmu.h"
+#include "smp.h"
+#include "pmu.h"
+
+cpumask_var_t xen_cpu_initialized_map;
+
+static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
+static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
+
+static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
+void asm_cpu_bringup_and_idle(void);
+
+static void cpu_bringup(void)
+{
+	int cpu;
+
+	cr4_init();
+	cpu_init();
+	fpu__init_cpu();
+	touch_softlockup_watchdog();
+
+	/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
+	if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
+		xen_enable_sysenter();
+		xen_enable_syscall();
+	}
+	cpu = smp_processor_id();
+	smp_store_cpu_info(cpu);
+	cpu_data(cpu).x86_max_cores = 1;
+	set_cpu_sibling_map(cpu);
+
+	speculative_store_bypass_ht_init();
+
+	xen_setup_cpu_clockevents();
+
+	notify_cpu_starting(cpu);
+
+	set_cpu_online(cpu, true);
+
+	cpu_set_state_online(cpu);  /* Implies full memory barrier. */
+
+	/* We can take interrupts now: we're officially "up". */
+	local_irq_enable();
+}
+
+asmlinkage __visible void cpu_bringup_and_idle(void)
+{
+	cpu_bringup();
+	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
+}
+
+void xen_smp_intr_free_pv(unsigned int cpu)
+{
+	kfree(per_cpu(xen_irq_work, cpu).name);
+	per_cpu(xen_irq_work, cpu).name = NULL;
+	if (per_cpu(xen_irq_work, cpu).irq >= 0) {
+		unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
+		per_cpu(xen_irq_work, cpu).irq = -1;
+	}
+
+	kfree(per_cpu(xen_pmu_irq, cpu).name);
+	per_cpu(xen_pmu_irq, cpu).name = NULL;
+	if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
+		unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
+		per_cpu(xen_pmu_irq, cpu).irq = -1;
+	}
+}
+
+int xen_smp_intr_init_pv(unsigned int cpu)
+{
+	int rc;
+	char *callfunc_name, *pmu_name;
+
+	callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
+	per_cpu(xen_irq_work, cpu).name = callfunc_name;
+	rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
+				    cpu,
+				    xen_irq_work_interrupt,
+				    IRQF_PERCPU|IRQF_NOBALANCING,
+				    callfunc_name,
+				    NULL);
+	if (rc < 0)
+		goto fail;
+	per_cpu(xen_irq_work, cpu).irq = rc;
+
+	if (is_xen_pmu) {
+		pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
+		per_cpu(xen_pmu_irq, cpu).name = pmu_name;
+		rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
+					     xen_pmu_irq_handler,
+					     IRQF_PERCPU|IRQF_NOBALANCING,
+					     pmu_name, NULL);
+		if (rc < 0)
+			goto fail;
+		per_cpu(xen_pmu_irq, cpu).irq = rc;
+	}
+
+	return 0;
+
+ fail:
+	xen_smp_intr_free_pv(cpu);
+	return rc;
+}
+
+static void __init _get_smp_config(unsigned int early)
+{
+	int i, rc;
+	unsigned int subtract = 0;
+
+	if (early)
+		return;
+
+	num_processors = 0;
+	disabled_cpus = 0;
+	for (i = 0; i < nr_cpu_ids; i++) {
+		rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
+		if (rc >= 0) {
+			num_processors++;
+			set_cpu_possible(i, true);
+		} else {
+			set_cpu_possible(i, false);
+			set_cpu_present(i, false);
+			subtract++;
+		}
+	}
+#ifdef CONFIG_HOTPLUG_CPU
+	/* This is akin to using 'nr_cpus' on the Linux command line.
+	 * Which is OK as when we use 'dom0_max_vcpus=X' we can only
+	 * have up to X, while nr_cpu_ids is greater than X. This
+	 * normally is not a problem, except when CPU hotplugging
+	 * is involved and then there might be more than X CPUs
+	 * in the guest - which will not work as there is no
+	 * hypercall to expand the max number of VCPUs an already
+	 * running guest has. So cap it up to X. */
+	if (subtract)
+		set_nr_cpu_ids(nr_cpu_ids - subtract);
+#endif
+
+}
+
+static void __init xen_pv_smp_prepare_boot_cpu(void)
+{
+	BUG_ON(smp_processor_id() != 0);
+	native_smp_prepare_boot_cpu();
+
+	if (!xen_feature(XENFEAT_writable_page_tables))
+		/* We've switched to the "real" per-cpu gdt, so make
+		 * sure the old memory can be recycled. */
+		make_lowmem_page_readwrite(xen_initial_gdt);
+
+	xen_setup_vcpu_info_placement();
+
+	/*
+	 * The alternative logic (which patches the unlock/lock) runs before
+	 * the smp bootup up code is activated. Hence we need to set this up
+	 * the core kernel is being patched. Otherwise we will have only
+	 * modules patched but not core code.
+	 */
+	xen_init_spinlocks();
+}
+
+static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
+{
+	unsigned cpu;
+
+	if (skip_ioapic_setup) {
+		char *m = (max_cpus == 0) ?
+			"The nosmp parameter is incompatible with Xen; " \
+			"use Xen dom0_max_vcpus=1 parameter" :
+			"The noapic parameter is incompatible with Xen";
+
+		xen_raw_printk(m);
+		panic(m);
+	}
+	xen_init_lock_cpu(0);
+
+	smp_prepare_cpus_common();
+
+	cpu_data(0).x86_max_cores = 1;
+
+	speculative_store_bypass_ht_init();
+
+	xen_pmu_init(0);
+
+	if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
+		BUG();
+
+	if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
+		panic("could not allocate xen_cpu_initialized_map\n");
+
+	cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
+
+	/* Restrict the possible_map according to max_cpus. */
+	while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
+		for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
+			continue;
+		set_cpu_possible(cpu, false);
+	}
+
+	for_each_possible_cpu(cpu)
+		set_cpu_present(cpu, true);
+}
+
+static int
+cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
+{
+	struct vcpu_guest_context *ctxt;
+	struct desc_struct *gdt;
+	unsigned long gdt_mfn;
+
+	/* used to tell cpu_init() that it can proceed with initialization */
+	cpumask_set_cpu(cpu, cpu_callout_mask);
+	if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
+		return 0;
+
+	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
+	if (ctxt == NULL) {
+		cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
+		cpumask_clear_cpu(cpu, cpu_callout_mask);
+		return -ENOMEM;
+	}
+
+	gdt = get_cpu_gdt_rw(cpu);
+
+	/*
+	 * Bring up the CPU in cpu_bringup_and_idle() with the stack
+	 * pointing just below where pt_regs would be if it were a normal
+	 * kernel entry.
+	 */
+	ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
+	ctxt->flags = VGCF_IN_KERNEL;
+	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
+	ctxt->user_regs.ds = __USER_DS;
+	ctxt->user_regs.es = __USER_DS;
+	ctxt->user_regs.ss = __KERNEL_DS;
+	ctxt->user_regs.cs = __KERNEL_CS;
+	ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
+
+	xen_copy_trap_info(ctxt->trap_ctxt);
+
+	BUG_ON((unsigned long)gdt & ~PAGE_MASK);
+
+	gdt_mfn = arbitrary_virt_to_mfn(gdt);
+	make_lowmem_page_readonly(gdt);
+	make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
+
+	ctxt->gdt_frames[0] = gdt_mfn;
+	ctxt->gdt_ents      = GDT_ENTRIES;
+
+	/*
+	 * Set SS:SP that Xen will use when entering guest kernel mode
+	 * from guest user mode.  Subsequent calls to load_sp0() can
+	 * change this value.
+	 */
+	ctxt->kernel_ss = __KERNEL_DS;
+	ctxt->kernel_sp = task_top_of_stack(idle);
+
+	ctxt->gs_base_kernel = per_cpu_offset(cpu);
+	ctxt->event_callback_eip    =
+		(unsigned long)xen_asm_exc_xen_hypervisor_callback;
+	ctxt->failsafe_callback_eip =
+		(unsigned long)xen_failsafe_callback;
+	per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
+
+	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
+	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
+		BUG();
+
+	kfree(ctxt);
+	return 0;
+}
+
+static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
+{
+	int rc;
+
+	rc = common_cpu_up(cpu, idle);
+	if (rc)
+		return rc;
+
+	xen_setup_runstate_info(cpu);
+
+	/*
+	 * PV VCPUs are always successfully taken down (see 'while' loop
+	 * in xen_cpu_die()), so -EBUSY is an error.
+	 */
+	rc = cpu_check_up_prepare(cpu);
+	if (rc)
+		return rc;
+
+	/* make sure interrupts start blocked */
+	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
+
+	rc = cpu_initialize_context(cpu, idle);
+	if (rc)
+		return rc;
+
+	xen_pmu_init(cpu);
+
+	rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
+	BUG_ON(rc);
+
+	while (cpu_report_state(cpu) != CPU_ONLINE)
+		HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
+
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int xen_pv_cpu_disable(void)
+{
+	unsigned int cpu = smp_processor_id();
+	if (cpu == 0)
+		return -EBUSY;
+
+	cpu_disable_common();
+
+	load_cr3(swapper_pg_dir);
+	return 0;
+}
+
+static void xen_pv_cpu_die(unsigned int cpu)
+{
+	while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
+				  xen_vcpu_nr(cpu), NULL)) {
+		__set_current_state(TASK_UNINTERRUPTIBLE);
+		schedule_timeout(HZ/10);
+	}
+
+	if (common_cpu_die(cpu) == 0) {
+		xen_smp_intr_free(cpu);
+		xen_uninit_lock_cpu(cpu);
+		xen_teardown_timer(cpu);
+		xen_pmu_finish(cpu);
+	}
+}
+
+static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
+{
+	play_dead_common();
+	HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
+	cpu_bringup();
+	/*
+	 * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
+	 * clears certain data that the cpu_idle loop (which called us
+	 * and that we return from) expects. The only way to get that
+	 * data back is to call:
+	 */
+	tick_nohz_idle_enter();
+	tick_nohz_idle_stop_tick_protected();
+
+	cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
+}
+
+#else /* !CONFIG_HOTPLUG_CPU */
+static int xen_pv_cpu_disable(void)
+{
+	return -ENOSYS;
+}
+
+static void xen_pv_cpu_die(unsigned int cpu)
+{
+	BUG();
+}
+
+static void xen_pv_play_dead(void)
+{
+	BUG();
+}
+
+#endif
+static void stop_self(void *v)
+{
+	int cpu = smp_processor_id();
+
+	/* make sure we're not pinning something down */
+	load_cr3(swapper_pg_dir);
+	/* should set up a minimal gdt */
+
+	set_cpu_online(cpu, false);
+
+	HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
+	BUG();
+}
+
+static void xen_pv_stop_other_cpus(int wait)
+{
+	smp_call_function(stop_self, NULL, wait);
+}
+
+static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
+{
+	irq_work_run();
+	inc_irq_stat(apic_irq_work_irqs);
+
+	return IRQ_HANDLED;
+}
+
+static const struct smp_ops xen_smp_ops __initconst = {
+	.smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
+	.smp_prepare_cpus = xen_pv_smp_prepare_cpus,
+	.smp_cpus_done = xen_smp_cpus_done,
+
+	.cpu_up = xen_pv_cpu_up,
+	.cpu_die = xen_pv_cpu_die,
+	.cpu_disable = xen_pv_cpu_disable,
+	.play_dead = xen_pv_play_dead,
+
+	.stop_other_cpus = xen_pv_stop_other_cpus,
+	.smp_send_reschedule = xen_smp_send_reschedule,
+
+	.send_call_func_ipi = xen_smp_send_call_function_ipi,
+	.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
+};
+
+void __init xen_smp_init(void)
+{
+	smp_ops = xen_smp_ops;
+
+	/* Avoid searching for BIOS MP tables */
+	x86_init.mpparse.find_smp_config = x86_init_noop;
+	x86_init.mpparse.get_smp_config = _get_smp_config;
+}