v4.19.13 snapshot.
diff --git a/arch/x86/xen/irq.c b/arch/x86/xen/irq.c
new file mode 100644
index 0000000..7515a19
--- /dev/null
+++ b/arch/x86/xen/irq.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/hardirq.h>
+
+#include <asm/x86_init.h>
+
+#include <xen/interface/xen.h>
+#include <xen/interface/sched.h>
+#include <xen/interface/vcpu.h>
+#include <xen/features.h>
+#include <xen/events.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/hypervisor.h>
+
+#include "xen-ops.h"
+
+/*
+ * Force a proper event-channel callback from Xen after clearing the
+ * callback mask. We do this in a very simple manner, by making a call
+ * down into Xen. The pending flag will be checked by Xen on return.
+ */
+void xen_force_evtchn_callback(void)
+{
+ (void)HYPERVISOR_xen_version(0, NULL);
+}
+
+asmlinkage __visible unsigned long xen_save_fl(void)
+{
+ struct vcpu_info *vcpu;
+ unsigned long flags;
+
+ vcpu = this_cpu_read(xen_vcpu);
+
+ /* flag has opposite sense of mask */
+ flags = !vcpu->evtchn_upcall_mask;
+
+ /* convert to IF type flag
+ -0 -> 0x00000000
+ -1 -> 0xffffffff
+ */
+ return (-flags) & X86_EFLAGS_IF;
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
+
+__visible void xen_restore_fl(unsigned long flags)
+{
+ struct vcpu_info *vcpu;
+
+ /* convert from IF type flag */
+ flags = !(flags & X86_EFLAGS_IF);
+
+ /* See xen_irq_enable() for why preemption must be disabled. */
+ preempt_disable();
+ vcpu = this_cpu_read(xen_vcpu);
+ vcpu->evtchn_upcall_mask = flags;
+
+ if (flags == 0) {
+ barrier(); /* unmask then check (avoid races) */
+ if (unlikely(vcpu->evtchn_upcall_pending))
+ xen_force_evtchn_callback();
+ preempt_enable();
+ } else
+ preempt_enable_no_resched();
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
+
+asmlinkage __visible void xen_irq_disable(void)
+{
+ /* There's a one instruction preempt window here. We need to
+ make sure we're don't switch CPUs between getting the vcpu
+ pointer and updating the mask. */
+ preempt_disable();
+ this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
+ preempt_enable_no_resched();
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
+
+asmlinkage __visible void xen_irq_enable(void)
+{
+ struct vcpu_info *vcpu;
+
+ /*
+ * We may be preempted as soon as vcpu->evtchn_upcall_mask is
+ * cleared, so disable preemption to ensure we check for
+ * events on the VCPU we are still running on.
+ */
+ preempt_disable();
+
+ vcpu = this_cpu_read(xen_vcpu);
+ vcpu->evtchn_upcall_mask = 0;
+
+ /* Doesn't matter if we get preempted here, because any
+ pending event will get dealt with anyway. */
+
+ barrier(); /* unmask then check (avoid races) */
+ if (unlikely(vcpu->evtchn_upcall_pending))
+ xen_force_evtchn_callback();
+
+ preempt_enable();
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
+
+static void xen_safe_halt(void)
+{
+ /* Blocking includes an implicit local_irq_enable(). */
+ if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
+ BUG();
+}
+
+static void xen_halt(void)
+{
+ if (irqs_disabled())
+ HYPERVISOR_vcpu_op(VCPUOP_down,
+ xen_vcpu_nr(smp_processor_id()), NULL);
+ else
+ xen_safe_halt();
+}
+
+static const struct pv_irq_ops xen_irq_ops __initconst = {
+ .save_fl = PV_CALLEE_SAVE(xen_save_fl),
+ .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
+ .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
+ .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
+
+ .safe_halt = xen_safe_halt,
+ .halt = xen_halt,
+};
+
+void __init xen_init_irq_ops(void)
+{
+ pv_irq_ops = xen_irq_ops;
+ x86_init.irqs.intr_init = xen_init_IRQ;
+}