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![Boris Ostrovsky](/assets/img/avatar_default.png)
If memory allocation in cpu_initialize_context() fails then it will bring up the VCPU and leave with the corresponding CPU bit set in xen_cpu_initialized_map. The following (presumably successful) CPU bring up will BUG in xen_pv_cpu_up() because nothing for that VCPU would be initialized. Clear the CPU bits, that were set in cpu_initialize_context() in case the memory allocation fails. [ bigeasy: Creating a patch from Boris' email. ] Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20220209080214.1439408-2-bigeasy@linutronix.de
469 lines
11 KiB
C
469 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Xen SMP support
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*
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* This file implements the Xen versions of smp_ops. SMP under Xen is
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* very straightforward. Bringing a CPU up is simply a matter of
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* loading its initial context and setting it running.
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*
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* IPIs are handled through the Xen event mechanism.
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*
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* Because virtual CPUs can be scheduled onto any real CPU, there's no
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* useful topology information for the kernel to make use of. As a
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* result, all CPUs are treated as if they're single-core and
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* single-threaded.
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*/
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#include <linux/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/smp.h>
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#include <linux/irq_work.h>
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#include <linux/tick.h>
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#include <linux/nmi.h>
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#include <linux/cpuhotplug.h>
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#include <linux/stackprotector.h>
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#include <linux/pgtable.h>
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#include <asm/paravirt.h>
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#include <asm/idtentry.h>
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#include <asm/desc.h>
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#include <asm/cpu.h>
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#include <asm/io_apic.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/vcpu.h>
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#include <xen/interface/xenpmu.h>
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#include <asm/spec-ctrl.h>
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#include <asm/xen/interface.h>
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#include <asm/xen/hypercall.h>
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#include <xen/xen.h>
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#include <xen/page.h>
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#include <xen/events.h>
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#include <xen/hvc-console.h>
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#include "xen-ops.h"
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#include "mmu.h"
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#include "smp.h"
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#include "pmu.h"
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cpumask_var_t xen_cpu_initialized_map;
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static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
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static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
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static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
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void asm_cpu_bringup_and_idle(void);
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static void cpu_bringup(void)
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{
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int cpu;
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cr4_init();
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cpu_init();
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touch_softlockup_watchdog();
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/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
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if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
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xen_enable_sysenter();
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xen_enable_syscall();
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}
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cpu = smp_processor_id();
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smp_store_cpu_info(cpu);
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cpu_data(cpu).x86_max_cores = 1;
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set_cpu_sibling_map(cpu);
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speculative_store_bypass_ht_init();
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xen_setup_cpu_clockevents();
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notify_cpu_starting(cpu);
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set_cpu_online(cpu, true);
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cpu_set_state_online(cpu); /* Implies full memory barrier. */
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/* We can take interrupts now: we're officially "up". */
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local_irq_enable();
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}
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asmlinkage __visible void cpu_bringup_and_idle(void)
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{
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cpu_bringup();
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cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
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}
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void xen_smp_intr_free_pv(unsigned int cpu)
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{
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if (per_cpu(xen_irq_work, cpu).irq >= 0) {
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unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
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per_cpu(xen_irq_work, cpu).irq = -1;
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kfree(per_cpu(xen_irq_work, cpu).name);
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per_cpu(xen_irq_work, cpu).name = NULL;
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}
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if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
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unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
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per_cpu(xen_pmu_irq, cpu).irq = -1;
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kfree(per_cpu(xen_pmu_irq, cpu).name);
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per_cpu(xen_pmu_irq, cpu).name = NULL;
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}
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}
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int xen_smp_intr_init_pv(unsigned int cpu)
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{
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int rc;
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char *callfunc_name, *pmu_name;
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callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
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rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
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cpu,
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xen_irq_work_interrupt,
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IRQF_PERCPU|IRQF_NOBALANCING,
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callfunc_name,
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NULL);
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if (rc < 0)
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goto fail;
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per_cpu(xen_irq_work, cpu).irq = rc;
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per_cpu(xen_irq_work, cpu).name = callfunc_name;
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if (is_xen_pmu) {
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pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
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rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
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xen_pmu_irq_handler,
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IRQF_PERCPU|IRQF_NOBALANCING,
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pmu_name, NULL);
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if (rc < 0)
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goto fail;
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per_cpu(xen_pmu_irq, cpu).irq = rc;
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per_cpu(xen_pmu_irq, cpu).name = pmu_name;
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}
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return 0;
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fail:
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xen_smp_intr_free_pv(cpu);
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return rc;
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}
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static void __init _get_smp_config(unsigned int early)
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{
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int i, rc;
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unsigned int subtract = 0;
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if (early)
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return;
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num_processors = 0;
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disabled_cpus = 0;
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for (i = 0; i < nr_cpu_ids; i++) {
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rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
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if (rc >= 0) {
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num_processors++;
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set_cpu_possible(i, true);
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} else {
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set_cpu_possible(i, false);
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set_cpu_present(i, false);
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subtract++;
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}
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}
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#ifdef CONFIG_HOTPLUG_CPU
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/* This is akin to using 'nr_cpus' on the Linux command line.
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* Which is OK as when we use 'dom0_max_vcpus=X' we can only
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* have up to X, while nr_cpu_ids is greater than X. This
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* normally is not a problem, except when CPU hotplugging
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* is involved and then there might be more than X CPUs
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* in the guest - which will not work as there is no
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* hypercall to expand the max number of VCPUs an already
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* running guest has. So cap it up to X. */
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if (subtract)
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nr_cpu_ids = nr_cpu_ids - subtract;
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#endif
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}
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static void __init xen_pv_smp_prepare_boot_cpu(void)
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{
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BUG_ON(smp_processor_id() != 0);
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native_smp_prepare_boot_cpu();
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if (!xen_feature(XENFEAT_writable_page_tables))
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/* We've switched to the "real" per-cpu gdt, so make
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* sure the old memory can be recycled. */
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make_lowmem_page_readwrite(xen_initial_gdt);
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xen_setup_vcpu_info_placement();
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/*
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* The alternative logic (which patches the unlock/lock) runs before
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* the smp bootup up code is activated. Hence we need to set this up
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* the core kernel is being patched. Otherwise we will have only
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* modules patched but not core code.
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*/
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xen_init_spinlocks();
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}
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static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
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{
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unsigned cpu;
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if (skip_ioapic_setup) {
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char *m = (max_cpus == 0) ?
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"The nosmp parameter is incompatible with Xen; " \
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"use Xen dom0_max_vcpus=1 parameter" :
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"The noapic parameter is incompatible with Xen";
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xen_raw_printk(m);
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panic(m);
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}
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xen_init_lock_cpu(0);
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smp_prepare_cpus_common();
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cpu_data(0).x86_max_cores = 1;
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speculative_store_bypass_ht_init();
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xen_pmu_init(0);
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if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
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BUG();
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if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
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panic("could not allocate xen_cpu_initialized_map\n");
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cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
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/* Restrict the possible_map according to max_cpus. */
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while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
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for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
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continue;
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set_cpu_possible(cpu, false);
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}
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for_each_possible_cpu(cpu)
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set_cpu_present(cpu, true);
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}
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static int
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cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
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{
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struct vcpu_guest_context *ctxt;
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struct desc_struct *gdt;
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unsigned long gdt_mfn;
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/* used to tell cpu_init() that it can proceed with initialization */
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cpumask_set_cpu(cpu, cpu_callout_mask);
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if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
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return 0;
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ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
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if (ctxt == NULL) {
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cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
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cpumask_clear_cpu(cpu, cpu_callout_mask);
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return -ENOMEM;
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}
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gdt = get_cpu_gdt_rw(cpu);
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/*
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* Bring up the CPU in cpu_bringup_and_idle() with the stack
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* pointing just below where pt_regs would be if it were a normal
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* kernel entry.
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*/
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ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
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ctxt->flags = VGCF_IN_KERNEL;
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ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
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ctxt->user_regs.ds = __USER_DS;
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ctxt->user_regs.es = __USER_DS;
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ctxt->user_regs.ss = __KERNEL_DS;
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ctxt->user_regs.cs = __KERNEL_CS;
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ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
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xen_copy_trap_info(ctxt->trap_ctxt);
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BUG_ON((unsigned long)gdt & ~PAGE_MASK);
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gdt_mfn = arbitrary_virt_to_mfn(gdt);
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make_lowmem_page_readonly(gdt);
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make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
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ctxt->gdt_frames[0] = gdt_mfn;
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ctxt->gdt_ents = GDT_ENTRIES;
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/*
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* Set SS:SP that Xen will use when entering guest kernel mode
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* from guest user mode. Subsequent calls to load_sp0() can
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* change this value.
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*/
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ctxt->kernel_ss = __KERNEL_DS;
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ctxt->kernel_sp = task_top_of_stack(idle);
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ctxt->gs_base_kernel = per_cpu_offset(cpu);
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ctxt->event_callback_eip =
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(unsigned long)xen_asm_exc_xen_hypervisor_callback;
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ctxt->failsafe_callback_eip =
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(unsigned long)xen_failsafe_callback;
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per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
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ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
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if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
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BUG();
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kfree(ctxt);
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return 0;
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}
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static int xen_pv_cpu_up(unsigned int cpu, struct task_struct *idle)
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{
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int rc;
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rc = common_cpu_up(cpu, idle);
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if (rc)
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return rc;
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xen_setup_runstate_info(cpu);
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/*
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* PV VCPUs are always successfully taken down (see 'while' loop
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* in xen_cpu_die()), so -EBUSY is an error.
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*/
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rc = cpu_check_up_prepare(cpu);
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if (rc)
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return rc;
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/* make sure interrupts start blocked */
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per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
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rc = cpu_initialize_context(cpu, idle);
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if (rc)
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return rc;
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xen_pmu_init(cpu);
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rc = HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL);
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BUG_ON(rc);
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while (cpu_report_state(cpu) != CPU_ONLINE)
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HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
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return 0;
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static int xen_pv_cpu_disable(void)
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{
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unsigned int cpu = smp_processor_id();
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if (cpu == 0)
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return -EBUSY;
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cpu_disable_common();
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load_cr3(swapper_pg_dir);
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return 0;
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}
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static void xen_pv_cpu_die(unsigned int cpu)
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{
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while (HYPERVISOR_vcpu_op(VCPUOP_is_up,
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xen_vcpu_nr(cpu), NULL)) {
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__set_current_state(TASK_UNINTERRUPTIBLE);
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schedule_timeout(HZ/10);
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}
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if (common_cpu_die(cpu) == 0) {
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xen_smp_intr_free(cpu);
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xen_uninit_lock_cpu(cpu);
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xen_teardown_timer(cpu);
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xen_pmu_finish(cpu);
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}
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}
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static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
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{
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play_dead_common();
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HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
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cpu_bringup();
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/*
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* commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down)
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* clears certain data that the cpu_idle loop (which called us
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* and that we return from) expects. The only way to get that
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* data back is to call:
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*/
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tick_nohz_idle_enter();
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tick_nohz_idle_stop_tick_protected();
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cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE);
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}
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#else /* !CONFIG_HOTPLUG_CPU */
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static int xen_pv_cpu_disable(void)
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{
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return -ENOSYS;
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}
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static void xen_pv_cpu_die(unsigned int cpu)
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{
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BUG();
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}
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static void xen_pv_play_dead(void)
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{
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BUG();
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}
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#endif
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static void stop_self(void *v)
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{
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int cpu = smp_processor_id();
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/* make sure we're not pinning something down */
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load_cr3(swapper_pg_dir);
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/* should set up a minimal gdt */
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set_cpu_online(cpu, false);
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HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
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BUG();
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}
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static void xen_pv_stop_other_cpus(int wait)
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{
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smp_call_function(stop_self, NULL, wait);
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}
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static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
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{
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irq_work_run();
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inc_irq_stat(apic_irq_work_irqs);
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return IRQ_HANDLED;
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}
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static const struct smp_ops xen_smp_ops __initconst = {
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.smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
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.smp_prepare_cpus = xen_pv_smp_prepare_cpus,
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.smp_cpus_done = xen_smp_cpus_done,
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.cpu_up = xen_pv_cpu_up,
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.cpu_die = xen_pv_cpu_die,
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.cpu_disable = xen_pv_cpu_disable,
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.play_dead = xen_pv_play_dead,
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.stop_other_cpus = xen_pv_stop_other_cpus,
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.smp_send_reschedule = xen_smp_send_reschedule,
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.send_call_func_ipi = xen_smp_send_call_function_ipi,
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.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
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};
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void __init xen_smp_init(void)
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{
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smp_ops = xen_smp_ops;
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/* Avoid searching for BIOS MP tables */
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x86_init.mpparse.find_smp_config = x86_init_noop;
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x86_init.mpparse.get_smp_config = _get_smp_config;
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}
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