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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2009, Microsoft Corporation.
4 *
5 * Authors:
6 * Haiyang Zhang <haiyangz@microsoft.com>
7 * Hank Janssen <hjanssen@microsoft.com>
8 */
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/kernel.h>
12#include <linux/mm.h>
13#include <linux/slab.h>
14#include <linux/vmalloc.h>
15#include <linux/hyperv.h>
16#include <linux/version.h>
17#include <linux/random.h>
18#include <linux/clockchips.h>
19#include <clocksource/hyperv_timer.h>
20#include <asm/mshyperv.h>
21#include "hyperv_vmbus.h"
22
23/* The one and only */
24struct hv_context hv_context;
25
26/*
27 * hv_init - Main initialization routine.
28 *
29 * This routine must be called before any other routines in here are called
30 */
31int hv_init(void)
32{
33 hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
34 if (!hv_context.cpu_context)
35 return -ENOMEM;
36 return 0;
37}
38
39/*
40 * hv_post_message - Post a message using the hypervisor message IPC.
41 *
42 * This involves a hypercall.
43 */
44int hv_post_message(union hv_connection_id connection_id,
45 enum hv_message_type message_type,
46 void *payload, size_t payload_size)
47{
48 struct hv_input_post_message *aligned_msg;
49 struct hv_per_cpu_context *hv_cpu;
50 u64 status;
51
52 if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
53 return -EMSGSIZE;
54
55 hv_cpu = get_cpu_ptr(hv_context.cpu_context);
56 aligned_msg = hv_cpu->post_msg_page;
57 aligned_msg->connectionid = connection_id;
58 aligned_msg->reserved = 0;
59 aligned_msg->message_type = message_type;
60 aligned_msg->payload_size = payload_size;
61 memcpy((void *)aligned_msg->payload, payload, payload_size);
62
63 status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);
64
65 /* Preemption must remain disabled until after the hypercall
66 * so some other thread can't get scheduled onto this cpu and
67 * corrupt the per-cpu post_msg_page
68 */
69 put_cpu_ptr(hv_cpu);
70
71 return status & 0xFFFF;
72}
73
74int hv_synic_alloc(void)
75{
76 int cpu;
77 struct hv_per_cpu_context *hv_cpu;
78
79 /*
80 * First, zero all per-cpu memory areas so hv_synic_free() can
81 * detect what memory has been allocated and cleanup properly
82 * after any failures.
83 */
84 for_each_present_cpu(cpu) {
85 hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
86 memset(hv_cpu, 0, sizeof(*hv_cpu));
87 }
88
89 hv_context.hv_numa_map = kcalloc(nr_node_ids, sizeof(struct cpumask),
90 GFP_KERNEL);
91 if (hv_context.hv_numa_map == NULL) {
92 pr_err("Unable to allocate NUMA map\n");
93 goto err;
94 }
95
96 for_each_present_cpu(cpu) {
97 hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
98
99 tasklet_init(&hv_cpu->msg_dpc,
100 vmbus_on_msg_dpc, (unsigned long) hv_cpu);
101
102 hv_cpu->synic_message_page =
103 (void *)get_zeroed_page(GFP_ATOMIC);
104 if (hv_cpu->synic_message_page == NULL) {
105 pr_err("Unable to allocate SYNIC message page\n");
106 goto err;
107 }
108
109 hv_cpu->synic_event_page = (void *)get_zeroed_page(GFP_ATOMIC);
110 if (hv_cpu->synic_event_page == NULL) {
111 pr_err("Unable to allocate SYNIC event page\n");
112 goto err;
113 }
114
115 hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
116 if (hv_cpu->post_msg_page == NULL) {
117 pr_err("Unable to allocate post msg page\n");
118 goto err;
119 }
120 }
121
122 return 0;
123err:
124 /*
125 * Any memory allocations that succeeded will be freed when
126 * the caller cleans up by calling hv_synic_free()
127 */
128 return -ENOMEM;
129}
130
131
132void hv_synic_free(void)
133{
134 int cpu;
135
136 for_each_present_cpu(cpu) {
137 struct hv_per_cpu_context *hv_cpu
138 = per_cpu_ptr(hv_context.cpu_context, cpu);
139
140 free_page((unsigned long)hv_cpu->synic_event_page);
141 free_page((unsigned long)hv_cpu->synic_message_page);
142 free_page((unsigned long)hv_cpu->post_msg_page);
143 }
144
145 kfree(hv_context.hv_numa_map);
146}
147
148/*
149 * hv_synic_init - Initialize the Synthetic Interrupt Controller.
150 *
151 * If it is already initialized by another entity (ie x2v shim), we need to
152 * retrieve the initialized message and event pages. Otherwise, we create and
153 * initialize the message and event pages.
154 */
155void hv_synic_enable_regs(unsigned int cpu)
156{
157 struct hv_per_cpu_context *hv_cpu
158 = per_cpu_ptr(hv_context.cpu_context, cpu);
159 union hv_synic_simp simp;
160 union hv_synic_siefp siefp;
161 union hv_synic_sint shared_sint;
162 union hv_synic_scontrol sctrl;
163
164 /* Setup the Synic's message page */
165 hv_get_simp(simp.as_uint64);
166 simp.simp_enabled = 1;
167 simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
168 >> PAGE_SHIFT;
169
170 hv_set_simp(simp.as_uint64);
171
172 /* Setup the Synic's event page */
173 hv_get_siefp(siefp.as_uint64);
174 siefp.siefp_enabled = 1;
175 siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
176 >> PAGE_SHIFT;
177
178 hv_set_siefp(siefp.as_uint64);
179
180 /* Setup the shared SINT. */
181 hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
182
183 shared_sint.vector = HYPERVISOR_CALLBACK_VECTOR;
184 shared_sint.masked = false;
185 shared_sint.auto_eoi = hv_recommend_using_aeoi();
186 hv_set_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
187
188 /* Enable the global synic bit */
189 hv_get_synic_state(sctrl.as_uint64);
190 sctrl.enable = 1;
191
192 hv_set_synic_state(sctrl.as_uint64);
193}
194
195int hv_synic_init(unsigned int cpu)
196{
197 hv_synic_enable_regs(cpu);
198
199 hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
200
201 return 0;
202}
203
204/*
205 * hv_synic_cleanup - Cleanup routine for hv_synic_init().
206 */
207void hv_synic_disable_regs(unsigned int cpu)
208{
209 union hv_synic_sint shared_sint;
210 union hv_synic_simp simp;
211 union hv_synic_siefp siefp;
212 union hv_synic_scontrol sctrl;
213
214 hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
215
216 shared_sint.masked = 1;
217
218 /* Need to correctly cleanup in the case of SMP!!! */
219 /* Disable the interrupt */
220 hv_set_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
221
222 hv_get_simp(simp.as_uint64);
223 simp.simp_enabled = 0;
224 simp.base_simp_gpa = 0;
225
226 hv_set_simp(simp.as_uint64);
227
228 hv_get_siefp(siefp.as_uint64);
229 siefp.siefp_enabled = 0;
230 siefp.base_siefp_gpa = 0;
231
232 hv_set_siefp(siefp.as_uint64);
233
234 /* Disable the global synic bit */
235 hv_get_synic_state(sctrl.as_uint64);
236 sctrl.enable = 0;
237 hv_set_synic_state(sctrl.as_uint64);
238}
239
240int hv_synic_cleanup(unsigned int cpu)
241{
242 struct vmbus_channel *channel, *sc;
243 bool channel_found = false;
244
245 /*
246 * Hyper-V does not provide a way to change the connect CPU once
247 * it is set; we must prevent the connect CPU from going offline.
248 */
249 if (cpu == VMBUS_CONNECT_CPU)
250 return -EBUSY;
251
252 /*
253 * Search for channels which are bound to the CPU we're about to
254 * cleanup. In case we find one and vmbus is still connected, we
255 * fail; this will effectively prevent CPU offlining.
256 *
257 * TODO: Re-bind the channels to different CPUs.
258 */
259 mutex_lock(&vmbus_connection.channel_mutex);
260 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
261 if (channel->target_cpu == cpu) {
262 channel_found = true;
263 break;
264 }
265 list_for_each_entry(sc, &channel->sc_list, sc_list) {
266 if (sc->target_cpu == cpu) {
267 channel_found = true;
268 break;
269 }
270 }
271 if (channel_found)
272 break;
273 }
274 mutex_unlock(&vmbus_connection.channel_mutex);
275
276 if (channel_found && vmbus_connection.conn_state == CONNECTED)
277 return -EBUSY;
278
279 hv_stimer_legacy_cleanup(cpu);
280
281 hv_synic_disable_regs(cpu);
282
283 return 0;
284}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2009, Microsoft Corporation.
4 *
5 * Authors:
6 * Haiyang Zhang <haiyangz@microsoft.com>
7 * Hank Janssen <hjanssen@microsoft.com>
8 */
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/io.h>
12#include <linux/kernel.h>
13#include <linux/mm.h>
14#include <linux/slab.h>
15#include <linux/vmalloc.h>
16#include <linux/hyperv.h>
17#include <linux/random.h>
18#include <linux/clockchips.h>
19#include <linux/delay.h>
20#include <linux/interrupt.h>
21#include <clocksource/hyperv_timer.h>
22#include <asm/mshyperv.h>
23#include "hyperv_vmbus.h"
24
25/* The one and only */
26struct hv_context hv_context;
27
28/*
29 * hv_init - Main initialization routine.
30 *
31 * This routine must be called before any other routines in here are called
32 */
33int hv_init(void)
34{
35 hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
36 if (!hv_context.cpu_context)
37 return -ENOMEM;
38 return 0;
39}
40
41/*
42 * Functions for allocating and freeing memory with size and
43 * alignment HV_HYP_PAGE_SIZE. These functions are needed because
44 * the guest page size may not be the same as the Hyper-V page
45 * size. We depend upon kmalloc() aligning power-of-two size
46 * allocations to the allocation size boundary, so that the
47 * allocated memory appears to Hyper-V as a page of the size
48 * it expects.
49 */
50
51void *hv_alloc_hyperv_page(void)
52{
53 BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
54
55 if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
56 return (void *)__get_free_page(GFP_KERNEL);
57 else
58 return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
59}
60
61void *hv_alloc_hyperv_zeroed_page(void)
62{
63 if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
64 return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
65 else
66 return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
67}
68
69void hv_free_hyperv_page(unsigned long addr)
70{
71 if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
72 free_page(addr);
73 else
74 kfree((void *)addr);
75}
76
77/*
78 * hv_post_message - Post a message using the hypervisor message IPC.
79 *
80 * This involves a hypercall.
81 */
82int hv_post_message(union hv_connection_id connection_id,
83 enum hv_message_type message_type,
84 void *payload, size_t payload_size)
85{
86 struct hv_input_post_message *aligned_msg;
87 struct hv_per_cpu_context *hv_cpu;
88 u64 status;
89
90 if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT)
91 return -EMSGSIZE;
92
93 hv_cpu = get_cpu_ptr(hv_context.cpu_context);
94 aligned_msg = hv_cpu->post_msg_page;
95 aligned_msg->connectionid = connection_id;
96 aligned_msg->reserved = 0;
97 aligned_msg->message_type = message_type;
98 aligned_msg->payload_size = payload_size;
99 memcpy((void *)aligned_msg->payload, payload, payload_size);
100
101 if (hv_isolation_type_snp())
102 status = hv_ghcb_hypercall(HVCALL_POST_MESSAGE,
103 (void *)aligned_msg, NULL,
104 sizeof(*aligned_msg));
105 else
106 status = hv_do_hypercall(HVCALL_POST_MESSAGE,
107 aligned_msg, NULL);
108
109 /* Preemption must remain disabled until after the hypercall
110 * so some other thread can't get scheduled onto this cpu and
111 * corrupt the per-cpu post_msg_page
112 */
113 put_cpu_ptr(hv_cpu);
114
115 return hv_result(status);
116}
117
118int hv_synic_alloc(void)
119{
120 int cpu;
121 struct hv_per_cpu_context *hv_cpu;
122
123 /*
124 * First, zero all per-cpu memory areas so hv_synic_free() can
125 * detect what memory has been allocated and cleanup properly
126 * after any failures.
127 */
128 for_each_present_cpu(cpu) {
129 hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
130 memset(hv_cpu, 0, sizeof(*hv_cpu));
131 }
132
133 hv_context.hv_numa_map = kcalloc(nr_node_ids, sizeof(struct cpumask),
134 GFP_KERNEL);
135 if (hv_context.hv_numa_map == NULL) {
136 pr_err("Unable to allocate NUMA map\n");
137 goto err;
138 }
139
140 for_each_present_cpu(cpu) {
141 hv_cpu = per_cpu_ptr(hv_context.cpu_context, cpu);
142
143 tasklet_init(&hv_cpu->msg_dpc,
144 vmbus_on_msg_dpc, (unsigned long) hv_cpu);
145
146 /*
147 * Synic message and event pages are allocated by paravisor.
148 * Skip these pages allocation here.
149 */
150 if (!hv_isolation_type_snp()) {
151 hv_cpu->synic_message_page =
152 (void *)get_zeroed_page(GFP_ATOMIC);
153 if (hv_cpu->synic_message_page == NULL) {
154 pr_err("Unable to allocate SYNIC message page\n");
155 goto err;
156 }
157
158 hv_cpu->synic_event_page =
159 (void *)get_zeroed_page(GFP_ATOMIC);
160 if (hv_cpu->synic_event_page == NULL) {
161 pr_err("Unable to allocate SYNIC event page\n");
162 goto err;
163 }
164 }
165
166 hv_cpu->post_msg_page = (void *)get_zeroed_page(GFP_ATOMIC);
167 if (hv_cpu->post_msg_page == NULL) {
168 pr_err("Unable to allocate post msg page\n");
169 goto err;
170 }
171 }
172
173 return 0;
174err:
175 /*
176 * Any memory allocations that succeeded will be freed when
177 * the caller cleans up by calling hv_synic_free()
178 */
179 return -ENOMEM;
180}
181
182
183void hv_synic_free(void)
184{
185 int cpu;
186
187 for_each_present_cpu(cpu) {
188 struct hv_per_cpu_context *hv_cpu
189 = per_cpu_ptr(hv_context.cpu_context, cpu);
190
191 free_page((unsigned long)hv_cpu->synic_event_page);
192 free_page((unsigned long)hv_cpu->synic_message_page);
193 free_page((unsigned long)hv_cpu->post_msg_page);
194 }
195
196 kfree(hv_context.hv_numa_map);
197}
198
199/*
200 * hv_synic_init - Initialize the Synthetic Interrupt Controller.
201 *
202 * If it is already initialized by another entity (ie x2v shim), we need to
203 * retrieve the initialized message and event pages. Otherwise, we create and
204 * initialize the message and event pages.
205 */
206void hv_synic_enable_regs(unsigned int cpu)
207{
208 struct hv_per_cpu_context *hv_cpu
209 = per_cpu_ptr(hv_context.cpu_context, cpu);
210 union hv_synic_simp simp;
211 union hv_synic_siefp siefp;
212 union hv_synic_sint shared_sint;
213 union hv_synic_scontrol sctrl;
214
215 /* Setup the Synic's message page */
216 simp.as_uint64 = hv_get_register(HV_REGISTER_SIMP);
217 simp.simp_enabled = 1;
218
219 if (hv_isolation_type_snp()) {
220 hv_cpu->synic_message_page
221 = memremap(simp.base_simp_gpa << HV_HYP_PAGE_SHIFT,
222 HV_HYP_PAGE_SIZE, MEMREMAP_WB);
223 if (!hv_cpu->synic_message_page)
224 pr_err("Fail to map syinc message page.\n");
225 } else {
226 simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
227 >> HV_HYP_PAGE_SHIFT;
228 }
229
230 hv_set_register(HV_REGISTER_SIMP, simp.as_uint64);
231
232 /* Setup the Synic's event page */
233 siefp.as_uint64 = hv_get_register(HV_REGISTER_SIEFP);
234 siefp.siefp_enabled = 1;
235
236 if (hv_isolation_type_snp()) {
237 hv_cpu->synic_event_page =
238 memremap(siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT,
239 HV_HYP_PAGE_SIZE, MEMREMAP_WB);
240
241 if (!hv_cpu->synic_event_page)
242 pr_err("Fail to map syinc event page.\n");
243 } else {
244 siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
245 >> HV_HYP_PAGE_SHIFT;
246 }
247
248 hv_set_register(HV_REGISTER_SIEFP, siefp.as_uint64);
249
250 /* Setup the shared SINT. */
251 if (vmbus_irq != -1)
252 enable_percpu_irq(vmbus_irq, 0);
253 shared_sint.as_uint64 = hv_get_register(HV_REGISTER_SINT0 +
254 VMBUS_MESSAGE_SINT);
255
256 shared_sint.vector = vmbus_interrupt;
257 shared_sint.masked = false;
258
259 /*
260 * On architectures where Hyper-V doesn't support AEOI (e.g., ARM64),
261 * it doesn't provide a recommendation flag and AEOI must be disabled.
262 */
263#ifdef HV_DEPRECATING_AEOI_RECOMMENDED
264 shared_sint.auto_eoi =
265 !(ms_hyperv.hints & HV_DEPRECATING_AEOI_RECOMMENDED);
266#else
267 shared_sint.auto_eoi = 0;
268#endif
269 hv_set_register(HV_REGISTER_SINT0 + VMBUS_MESSAGE_SINT,
270 shared_sint.as_uint64);
271
272 /* Enable the global synic bit */
273 sctrl.as_uint64 = hv_get_register(HV_REGISTER_SCONTROL);
274 sctrl.enable = 1;
275
276 hv_set_register(HV_REGISTER_SCONTROL, sctrl.as_uint64);
277}
278
279int hv_synic_init(unsigned int cpu)
280{
281 hv_synic_enable_regs(cpu);
282
283 hv_stimer_legacy_init(cpu, VMBUS_MESSAGE_SINT);
284
285 return 0;
286}
287
288/*
289 * hv_synic_cleanup - Cleanup routine for hv_synic_init().
290 */
291void hv_synic_disable_regs(unsigned int cpu)
292{
293 struct hv_per_cpu_context *hv_cpu
294 = per_cpu_ptr(hv_context.cpu_context, cpu);
295 union hv_synic_sint shared_sint;
296 union hv_synic_simp simp;
297 union hv_synic_siefp siefp;
298 union hv_synic_scontrol sctrl;
299
300 shared_sint.as_uint64 = hv_get_register(HV_REGISTER_SINT0 +
301 VMBUS_MESSAGE_SINT);
302
303 shared_sint.masked = 1;
304
305 /* Need to correctly cleanup in the case of SMP!!! */
306 /* Disable the interrupt */
307 hv_set_register(HV_REGISTER_SINT0 + VMBUS_MESSAGE_SINT,
308 shared_sint.as_uint64);
309
310 simp.as_uint64 = hv_get_register(HV_REGISTER_SIMP);
311 /*
312 * In Isolation VM, sim and sief pages are allocated by
313 * paravisor. These pages also will be used by kdump
314 * kernel. So just reset enable bit here and keep page
315 * addresses.
316 */
317 simp.simp_enabled = 0;
318 if (hv_isolation_type_snp())
319 memunmap(hv_cpu->synic_message_page);
320 else
321 simp.base_simp_gpa = 0;
322
323 hv_set_register(HV_REGISTER_SIMP, simp.as_uint64);
324
325 siefp.as_uint64 = hv_get_register(HV_REGISTER_SIEFP);
326 siefp.siefp_enabled = 0;
327
328 if (hv_isolation_type_snp())
329 memunmap(hv_cpu->synic_event_page);
330 else
331 siefp.base_siefp_gpa = 0;
332
333 hv_set_register(HV_REGISTER_SIEFP, siefp.as_uint64);
334
335 /* Disable the global synic bit */
336 sctrl.as_uint64 = hv_get_register(HV_REGISTER_SCONTROL);
337 sctrl.enable = 0;
338 hv_set_register(HV_REGISTER_SCONTROL, sctrl.as_uint64);
339
340 if (vmbus_irq != -1)
341 disable_percpu_irq(vmbus_irq);
342}
343
344#define HV_MAX_TRIES 3
345/*
346 * Scan the event flags page of 'this' CPU looking for any bit that is set. If we find one
347 * bit set, then wait for a few milliseconds. Repeat these steps for a maximum of 3 times.
348 * Return 'true', if there is still any set bit after this operation; 'false', otherwise.
349 *
350 * If a bit is set, that means there is a pending channel interrupt. The expectation is
351 * that the normal interrupt handling mechanism will find and process the channel interrupt
352 * "very soon", and in the process clear the bit.
353 */
354static bool hv_synic_event_pending(void)
355{
356 struct hv_per_cpu_context *hv_cpu = this_cpu_ptr(hv_context.cpu_context);
357 union hv_synic_event_flags *event =
358 (union hv_synic_event_flags *)hv_cpu->synic_event_page + VMBUS_MESSAGE_SINT;
359 unsigned long *recv_int_page = event->flags; /* assumes VMBus version >= VERSION_WIN8 */
360 bool pending;
361 u32 relid;
362 int tries = 0;
363
364retry:
365 pending = false;
366 for_each_set_bit(relid, recv_int_page, HV_EVENT_FLAGS_COUNT) {
367 /* Special case - VMBus channel protocol messages */
368 if (relid == 0)
369 continue;
370 pending = true;
371 break;
372 }
373 if (pending && tries++ < HV_MAX_TRIES) {
374 usleep_range(10000, 20000);
375 goto retry;
376 }
377 return pending;
378}
379
380int hv_synic_cleanup(unsigned int cpu)
381{
382 struct vmbus_channel *channel, *sc;
383 bool channel_found = false;
384
385 if (vmbus_connection.conn_state != CONNECTED)
386 goto always_cleanup;
387
388 /*
389 * Hyper-V does not provide a way to change the connect CPU once
390 * it is set; we must prevent the connect CPU from going offline
391 * while the VM is running normally. But in the panic or kexec()
392 * path where the vmbus is already disconnected, the CPU must be
393 * allowed to shut down.
394 */
395 if (cpu == VMBUS_CONNECT_CPU)
396 return -EBUSY;
397
398 /*
399 * Search for channels which are bound to the CPU we're about to
400 * cleanup. In case we find one and vmbus is still connected, we
401 * fail; this will effectively prevent CPU offlining.
402 *
403 * TODO: Re-bind the channels to different CPUs.
404 */
405 mutex_lock(&vmbus_connection.channel_mutex);
406 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
407 if (channel->target_cpu == cpu) {
408 channel_found = true;
409 break;
410 }
411 list_for_each_entry(sc, &channel->sc_list, sc_list) {
412 if (sc->target_cpu == cpu) {
413 channel_found = true;
414 break;
415 }
416 }
417 if (channel_found)
418 break;
419 }
420 mutex_unlock(&vmbus_connection.channel_mutex);
421
422 if (channel_found)
423 return -EBUSY;
424
425 /*
426 * channel_found == false means that any channels that were previously
427 * assigned to the CPU have been reassigned elsewhere with a call of
428 * vmbus_send_modifychannel(). Scan the event flags page looking for
429 * bits that are set and waiting with a timeout for vmbus_chan_sched()
430 * to process such bits. If bits are still set after this operation
431 * and VMBus is connected, fail the CPU offlining operation.
432 */
433 if (vmbus_proto_version >= VERSION_WIN10_V4_1 && hv_synic_event_pending())
434 return -EBUSY;
435
436always_cleanup:
437 hv_stimer_legacy_cleanup(cpu);
438
439 hv_synic_disable_regs(cpu);
440
441 return 0;
442}