fee87e931c
commit 8645e56a4ad6dcbf504872db7f14a2f67db88ef2 upstream.
xen_maybe_preempt_hcall() is called from the exception entry point
xen_do_hypervisor_callback with interrupts disabled.
_cond_resched() evades the might_sleep() check in cond_resched() which
would have caught that and schedule_debug() unfortunately lacks a check
for irqs_disabled().
Enable interrupts around the call and use cond_resched() to catch future
issues.
Fixes: fdfd811ddd ("x86/xen: allow privcmd hypercalls to be preempted")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/878skypjrh.fsf@nanos.tec.linutronix.de
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
46 lines
1.2 KiB
C
46 lines
1.2 KiB
C
/*
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* Preemptible hypercalls
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*
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* Copyright (C) 2014 Citrix Systems R&D ltd.
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*
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* This source code is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*/
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#include <linux/sched.h>
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#include <xen/xen-ops.h>
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#ifndef CONFIG_PREEMPT
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/*
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* Some hypercalls issued by the toolstack can take many 10s of
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* seconds. Allow tasks running hypercalls via the privcmd driver to
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* be voluntarily preempted even if full kernel preemption is
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* disabled.
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*
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* Such preemptible hypercalls are bracketed by
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* xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()
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* calls.
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*/
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DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);
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EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
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asmlinkage __visible void xen_maybe_preempt_hcall(void)
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{
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if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
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&& need_resched())) {
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/*
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* Clear flag as we may be rescheduled on a different
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* cpu.
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*/
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__this_cpu_write(xen_in_preemptible_hcall, false);
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local_irq_enable();
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cond_resched();
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local_irq_disable();
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__this_cpu_write(xen_in_preemptible_hcall, true);
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}
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}
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#endif /* CONFIG_PREEMPT */
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