diff options
Diffstat (limited to 'arch/x86/entry/common.c')
| -rw-r--r-- | arch/x86/entry/common.c | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 066215a243b4..a0f8c3cb130a 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -27,6 +27,11 @@ #include <linux/syscalls.h> #include <linux/uaccess.h> +#ifdef CONFIG_XEN_PV +#include <xen/xen-ops.h> +#include <xen/events.h> +#endif + #include <asm/desc.h> #include <asm/traps.h> #include <asm/vdso.h> @@ -35,6 +40,7 @@ #include <asm/nospec-branch.h> #include <asm/io_bitmap.h> #include <asm/syscall.h> +#include <asm/irq_stack.h> #define CREATE_TRACE_POINTS #include <trace/events/syscalls.h> @@ -680,3 +686,75 @@ void noinstr idtentry_exit_user(struct pt_regs *regs) prepare_exit_to_usermode(regs); } + +#ifdef CONFIG_XEN_PV +#ifndef CONFIG_PREEMPTION +/* + * Some hypercalls issued by the toolstack can take many 10s of + * seconds. Allow tasks running hypercalls via the privcmd driver to + * be voluntarily preempted even if full kernel preemption is + * disabled. + * + * Such preemptible hypercalls are bracketed by + * xen_preemptible_hcall_begin() and xen_preemptible_hcall_end() + * calls. + */ +DEFINE_PER_CPU(bool, xen_in_preemptible_hcall); +EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall); + +/* + * In case of scheduling the flag must be cleared and restored after + * returning from schedule as the task might move to a different CPU. + */ +static __always_inline bool get_and_clear_inhcall(void) +{ + bool inhcall = __this_cpu_read(xen_in_preemptible_hcall); + + __this_cpu_write(xen_in_preemptible_hcall, false); + return inhcall; +} + +static __always_inline void restore_inhcall(bool inhcall) +{ + __this_cpu_write(xen_in_preemptible_hcall, inhcall); +} +#else +static __always_inline bool get_and_clear_inhcall(void) { return false; } +static __always_inline void restore_inhcall(bool inhcall) { } +#endif + +static void __xen_pv_evtchn_do_upcall(void) +{ + irq_enter_rcu(); + inc_irq_stat(irq_hv_callback_count); + + xen_hvm_evtchn_do_upcall(); + + irq_exit_rcu(); +} + +__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs) +{ + struct pt_regs *old_regs; + bool inhcall, rcu_exit; + + rcu_exit = idtentry_enter_cond_rcu(regs); + old_regs = set_irq_regs(regs); + + instrumentation_begin(); + run_on_irqstack_cond(__xen_pv_evtchn_do_upcall, NULL, regs); + instrumentation_begin(); + + set_irq_regs(old_regs); + + inhcall = get_and_clear_inhcall(); + if (inhcall && !WARN_ON_ONCE(rcu_exit)) { + instrumentation_begin(); + idtentry_exit_cond_resched(regs, true); + instrumentation_end(); + restore_inhcall(inhcall); + } else { + idtentry_exit_cond_rcu(regs, rcu_exit); + } +} +#endif /* CONFIG_XEN_PV */ |