tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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x86/hyperv: Skip LP/VP creation on kexec

After a kexec the logical processors and virtual processors already
exist in the hypervisor because they were created by the previous
kernel. Attempting to add them again causes either a BUG_ON or
corrupted VP state leading to MCEs in the new kernel.

Add hv_lp_exists() to probe whether an LP is already present by
calling HVCALL_GET_LOGICAL_PROCESSOR_RUN_TIME. When it succeeds the
LP exists and we skip the add-LP and create-VP loops entirely.

Also add hv_call_notify_all_processors_started() which informs the
hypervisor that all processors are online. This is required after
adding LPs (fresh boot) and is a no-op on kexec since we skip that
path.

Co-developed-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com>
Signed-off-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com>
Co-developed-by: Stanislav Kinsburskii <stanislav.kinsburskii@gmail.com>
Signed-off-by: Stanislav Kinsburskii <stanislav.kinsburskii@gmail.com>
Co-developed-by: Mukesh Rathor <mrathor@linux.microsoft.com>
Signed-off-by: Mukesh Rathor <mrathor@linux.microsoft.com>
Signed-off-by: Jork Loeser <jloeser@linux.microsoft.com>
Reviewed-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>

authored by

Jork Loeser and committed by
Wei Liu 5170a82e f7ce370b

+77
+7
arch/x86/kernel/cpu/mshyperv.c
··· 429 429 } 430 430 431 431 #ifdef CONFIG_X86_64 432 + /* If AP LPs exist, we are in a kexec'd kernel and VPs already exist */ 433 + if (num_present_cpus() == 1 || hv_lp_exists(1)) 434 + return; 435 + 432 436 for_each_present_cpu(i) { 433 437 if (i == 0) 434 438 continue; 435 439 ret = hv_call_add_logical_proc(numa_cpu_node(i), i, cpu_physical_id(i)); 436 440 BUG_ON(ret); 437 441 } 442 + 443 + ret = hv_call_notify_all_processors_started(); 444 + WARN_ON(ret); 438 445 439 446 for_each_present_cpu(i) { 440 447 if (i == 0)
+47
drivers/hv/hv_proc.c
··· 239 239 return ret; 240 240 } 241 241 EXPORT_SYMBOL_GPL(hv_call_create_vp); 242 + 243 + int hv_call_notify_all_processors_started(void) 244 + { 245 + struct hv_input_notify_partition_event *input; 246 + u64 status; 247 + unsigned long irq_flags; 248 + int ret = 0; 249 + 250 + local_irq_save(irq_flags); 251 + input = *this_cpu_ptr(hyperv_pcpu_input_arg); 252 + memset(input, 0, sizeof(*input)); 253 + input->event = HV_PARTITION_ALL_LOGICAL_PROCESSORS_STARTED; 254 + status = hv_do_hypercall(HVCALL_NOTIFY_PARTITION_EVENT, 255 + input, NULL); 256 + local_irq_restore(irq_flags); 257 + 258 + if (!hv_result_success(status)) { 259 + hv_status_err(status, "\n"); 260 + ret = hv_result_to_errno(status); 261 + } 262 + return ret; 263 + } 264 + 265 + bool hv_lp_exists(u32 lp_index) 266 + { 267 + struct hv_input_get_logical_processor_run_time *input; 268 + struct hv_output_get_logical_processor_run_time *output; 269 + unsigned long flags; 270 + u64 status; 271 + 272 + local_irq_save(flags); 273 + input = *this_cpu_ptr(hyperv_pcpu_input_arg); 274 + output = *this_cpu_ptr(hyperv_pcpu_output_arg); 275 + 276 + input->lp_index = lp_index; 277 + status = hv_do_hypercall(HVCALL_GET_LOGICAL_PROCESSOR_RUN_TIME, 278 + input, output); 279 + local_irq_restore(flags); 280 + 281 + if (!hv_result_success(status) && 282 + hv_result(status) != HV_STATUS_INVALID_LP_INDEX) { 283 + hv_status_err(status, "\n"); 284 + BUG(); 285 + } 286 + 287 + return hv_result_success(status); 288 + }
+10
include/asm-generic/mshyperv.h
··· 347 347 int hv_deposit_memory_node(int node, u64 partition_id, u64 status); 348 348 int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages); 349 349 int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id); 350 + int hv_call_notify_all_processors_started(void); 351 + bool hv_lp_exists(u32 lp_index); 350 352 int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags); 351 353 352 354 #else /* CONFIG_MSHV_ROOT */ ··· 367 365 static inline int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id) 368 366 { 369 367 return -EOPNOTSUPP; 368 + } 369 + static inline int hv_call_notify_all_processors_started(void) 370 + { 371 + return -EOPNOTSUPP; 372 + } 373 + static inline bool hv_lp_exists(u32 lp_index) 374 + { 375 + return false; 370 376 } 371 377 static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags) 372 378 {
+1
include/hyperv/hvgdk_mini.h
··· 435 435 /* HV_CALL_CODE */ 436 436 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE 0x0002 437 437 #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST 0x0003 438 + #define HVCALL_GET_LOGICAL_PROCESSOR_RUN_TIME 0x0004 438 439 #define HVCALL_NOTIFY_LONG_SPIN_WAIT 0x0008 439 440 #define HVCALL_SEND_IPI 0x000b 440 441 #define HVCALL_ENABLE_VP_VTL 0x000f
+12
include/hyperv/hvhdk_mini.h
··· 362 362 363 363 enum hv_partition_event { 364 364 HV_PARTITION_EVENT_ROOT_CRASHDUMP = 2, 365 + HV_PARTITION_ALL_LOGICAL_PROCESSORS_STARTED = 4, 365 366 }; 366 367 367 368 struct hv_input_notify_partition_event { 368 369 u32 event; /* enum hv_partition_event */ 369 370 union hv_partition_event_input input; 371 + } __packed; 372 + 373 + struct hv_input_get_logical_processor_run_time { 374 + u32 lp_index; 375 + } __packed; 376 + 377 + struct hv_output_get_logical_processor_run_time { 378 + u64 global_time; 379 + u64 local_run_time; 380 + u64 rsvdz0; 381 + u64 hypervisor_time; 370 382 } __packed; 371 383 372 384 struct hv_lp_startup_status {