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eed0574432
The sched_clock() can be used very early since commit857baa87b6("sched/clock: Enable sched clock early"). In addition, with commit38669ba205("x86/xen/time: Output xen sched_clock time from 0"), kdump kernel in Xen HVM guest may panic at very early stage when accessing &__this_cpu_read(xen_vcpu)->time as in below: setup_arch() -> init_hypervisor_platform() -> x86_init.hyper.init_platform = xen_hvm_guest_init() -> xen_hvm_init_time_ops() -> xen_clocksource_read() -> src = &__this_cpu_read(xen_vcpu)->time; This is because Xen HVM supports at most MAX_VIRT_CPUS=32 'vcpu_info' embedded inside 'shared_info' during early stage until xen_vcpu_setup() is used to allocate/relocate 'vcpu_info' for boot cpu at arbitrary address. However, when Xen HVM guest panic on vcpu >= 32, since xen_vcpu_info_reset(0) would set per_cpu(xen_vcpu, cpu) = NULL when vcpu >= 32, xen_clocksource_read() on vcpu >= 32 would panic. This patch calls xen_hvm_init_time_ops() again later in xen_hvm_smp_prepare_boot_cpu() after the 'vcpu_info' for boot vcpu is registered when the boot vcpu is >= 32. This issue can be reproduced on purpose via below command at the guest side when kdump/kexec is enabled: "taskset -c 33 echo c > /proc/sysrq-trigger" The bugfix for PVM is not implemented due to the lack of testing environment. [boris: xen_hvm_init_time_ops() returns on errors instead of jumping to end] Cc: Joe Jin <joe.jin@oracle.com> Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Link: https://lore.kernel.org/r/20220302164032.14569-3-dongli.zhang@oracle.com Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
92 lines
2 KiB
C
92 lines
2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/thread_info.h>
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#include <asm/smp.h>
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#include <xen/events.h>
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#include "xen-ops.h"
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#include "smp.h"
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static void __init xen_hvm_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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/*
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* Setup vcpu_info for boot CPU. Secondary CPUs get their vcpu_info
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* in xen_cpu_up_prepare_hvm().
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*/
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xen_vcpu_setup(0);
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/*
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* Called again in case the kernel boots on vcpu >= MAX_VIRT_CPUS.
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* Refer to comments in xen_hvm_init_time_ops().
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*/
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xen_hvm_init_time_ops();
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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_hvm_smp_prepare_cpus(unsigned int max_cpus)
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{
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int cpu;
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native_smp_prepare_cpus(max_cpus);
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if (xen_have_vector_callback) {
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WARN_ON(xen_smp_intr_init(0));
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xen_init_lock_cpu(0);
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}
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for_each_possible_cpu(cpu) {
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if (cpu == 0)
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continue;
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/* Set default vcpu_id to make sure that we don't use cpu-0's */
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per_cpu(xen_vcpu_id, cpu) = XEN_VCPU_ID_INVALID;
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}
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}
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#ifdef CONFIG_HOTPLUG_CPU
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static void xen_hvm_cpu_die(unsigned int cpu)
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{
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if (common_cpu_die(cpu) == 0) {
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if (xen_have_vector_callback) {
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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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}
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}
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}
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#else
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static void xen_hvm_cpu_die(unsigned int cpu)
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{
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BUG();
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}
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#endif
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void __init xen_hvm_smp_init(void)
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{
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smp_ops.smp_prepare_boot_cpu = xen_hvm_smp_prepare_boot_cpu;
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smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
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smp_ops.smp_cpus_done = xen_smp_cpus_done;
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smp_ops.cpu_die = xen_hvm_cpu_die;
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if (!xen_have_vector_callback) {
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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nopvspin = true;
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#endif
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return;
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}
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smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
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smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
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smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
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}
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