1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Preemptible hypercalls 4 * 5 * Copyright (C) 2014 Citrix Systems R&D ltd. 6 */ 7 8 #include <linux/sched.h> 9 #include <xen/xen-ops.h> 10 11 #ifndef CONFIG_PREEMPT 12 13 /* 14 * Some hypercalls issued by the toolstack can take many 10s of 15 * seconds. Allow tasks running hypercalls via the privcmd driver to 16 * be voluntarily preempted even if full kernel preemption is 17 * disabled. 18 * 19 * Such preemptible hypercalls are bracketed by 20 * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end() 21 * calls. 22 */ 23 24 DEFINE_PER_CPU(bool, xen_in_preemptible_hcall); 25 EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall); 26 xen_maybe_preempt_hcall(void)27asmlinkage __visible void xen_maybe_preempt_hcall(void) 28 { 29 if (unlikely(__this_cpu_read(xen_in_preemptible_hcall) 30 && need_resched())) { 31 /* 32 * Clear flag as we may be rescheduled on a different 33 * cpu. 34 */ 35 __this_cpu_write(xen_in_preemptible_hcall, false); 36 _cond_resched(); 37 __this_cpu_write(xen_in_preemptible_hcall, true); 38 } 39 } 40 #endif /* CONFIG_PREEMPT */ 41