1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/hardirq.h>
3
4 #include <asm/x86_init.h>
5
6 #include <xen/interface/xen.h>
7 #include <xen/interface/sched.h>
8 #include <xen/interface/vcpu.h>
9 #include <xen/features.h>
10 #include <xen/events.h>
11
12 #include <asm/xen/hypercall.h>
13 #include <asm/xen/hypervisor.h>
14
15 #include "xen-ops.h"
16
17 /*
18 * Force a proper event-channel callback from Xen after clearing the
19 * callback mask. We do this in a very simple manner, by making a call
20 * down into Xen. The pending flag will be checked by Xen on return.
21 */
xen_force_evtchn_callback(void)22 void xen_force_evtchn_callback(void)
23 {
24 (void)HYPERVISOR_xen_version(0, NULL);
25 }
26
xen_save_fl(void)27 asmlinkage __visible unsigned long xen_save_fl(void)
28 {
29 struct vcpu_info *vcpu;
30 unsigned long flags;
31
32 vcpu = this_cpu_read(xen_vcpu);
33
34 /* flag has opposite sense of mask */
35 flags = !vcpu->evtchn_upcall_mask;
36
37 /* convert to IF type flag
38 -0 -> 0x00000000
39 -1 -> 0xffffffff
40 */
41 return (-flags) & X86_EFLAGS_IF;
42 }
43 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
44
xen_restore_fl(unsigned long flags)45 __visible void xen_restore_fl(unsigned long flags)
46 {
47 struct vcpu_info *vcpu;
48
49 /* convert from IF type flag */
50 flags = !(flags & X86_EFLAGS_IF);
51
52 /* See xen_irq_enable() for why preemption must be disabled. */
53 preempt_disable();
54 vcpu = this_cpu_read(xen_vcpu);
55 vcpu->evtchn_upcall_mask = flags;
56
57 if (flags == 0) {
58 barrier(); /* unmask then check (avoid races) */
59 if (unlikely(vcpu->evtchn_upcall_pending))
60 xen_force_evtchn_callback();
61 preempt_enable();
62 } else
63 preempt_enable_no_resched();
64 }
65 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
66
xen_irq_disable(void)67 asmlinkage __visible void xen_irq_disable(void)
68 {
69 /* There's a one instruction preempt window here. We need to
70 make sure we're don't switch CPUs between getting the vcpu
71 pointer and updating the mask. */
72 preempt_disable();
73 this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
74 preempt_enable_no_resched();
75 }
76 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
77
xen_irq_enable(void)78 asmlinkage __visible void xen_irq_enable(void)
79 {
80 struct vcpu_info *vcpu;
81
82 /*
83 * We may be preempted as soon as vcpu->evtchn_upcall_mask is
84 * cleared, so disable preemption to ensure we check for
85 * events on the VCPU we are still running on.
86 */
87 preempt_disable();
88
89 vcpu = this_cpu_read(xen_vcpu);
90 vcpu->evtchn_upcall_mask = 0;
91
92 /* Doesn't matter if we get preempted here, because any
93 pending event will get dealt with anyway. */
94
95 barrier(); /* unmask then check (avoid races) */
96 if (unlikely(vcpu->evtchn_upcall_pending))
97 xen_force_evtchn_callback();
98
99 preempt_enable();
100 }
101 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
102
xen_safe_halt(void)103 static void xen_safe_halt(void)
104 {
105 /* Blocking includes an implicit local_irq_enable(). */
106 if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
107 BUG();
108 }
109
xen_halt(void)110 static void xen_halt(void)
111 {
112 if (irqs_disabled())
113 HYPERVISOR_vcpu_op(VCPUOP_down,
114 xen_vcpu_nr(smp_processor_id()), NULL);
115 else
116 xen_safe_halt();
117 }
118
119 static const struct pv_irq_ops xen_irq_ops __initconst = {
120 .save_fl = PV_CALLEE_SAVE(xen_save_fl),
121 .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
122 .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
123 .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
124
125 .safe_halt = xen_safe_halt,
126 .halt = xen_halt,
127 };
128
xen_init_irq_ops(void)129 void __init xen_init_irq_ops(void)
130 {
131 pv_irq_ops = xen_irq_ops;
132 x86_init.irqs.intr_init = xen_init_IRQ;
133 }
134
