Commit 5170a82e authored by Jork Loeser's avatar Jork Loeser Committed by Wei Liu
Browse files

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: default avatarAnirudh Rayabharam <anrayabh@linux.microsoft.com>
Signed-off-by: default avatarAnirudh Rayabharam <anrayabh@linux.microsoft.com>
Co-developed-by: default avatarStanislav Kinsburskii <stanislav.kinsburskii@gmail.com>
Signed-off-by: default avatarStanislav Kinsburskii <stanislav.kinsburskii@gmail.com>
Co-developed-by: default avatarMukesh Rathor <mrathor@linux.microsoft.com>
Signed-off-by: default avatarMukesh Rathor <mrathor@linux.microsoft.com>
Signed-off-by: default avatarJork Loeser <jloeser@linux.microsoft.com>
Reviewed-by: default avatarStanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Signed-off-by: default avatarWei Liu <wei.liu@kernel.org>
parent f7ce370b

arch/x86/kernel/cpu/mshyperv.c

+7 −0
Original line number Diff line number Diff line
@@ -429,6 +429,10 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus) 
	}



#ifdef CONFIG_X86_64

	/* If AP LPs exist, we are in a kexec'd kernel and VPs already exist */

	if (num_present_cpus() == 1 || hv_lp_exists(1))

		return;



	for_each_present_cpu(i) {

		if (i == 0)

			continue;
@@ -436,6 +440,9 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus) 
		BUG_ON(ret);

	}



	ret = hv_call_notify_all_processors_started();

	WARN_ON(ret);



	for_each_present_cpu(i) {

		if (i == 0)

			continue;

drivers/hv/hv_proc.c

+47 −0
Original line number Diff line number Diff line
@@ -239,3 +239,50 @@ int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags) 
	return ret;

}

EXPORT_SYMBOL_GPL(hv_call_create_vp);



int hv_call_notify_all_processors_started(void)

{

	struct hv_input_notify_partition_event *input;

	u64 status;

	unsigned long irq_flags;

	int ret = 0;



	local_irq_save(irq_flags);

	input = *this_cpu_ptr(hyperv_pcpu_input_arg);

	memset(input, 0, sizeof(*input));

	input->event = HV_PARTITION_ALL_LOGICAL_PROCESSORS_STARTED;

	status = hv_do_hypercall(HVCALL_NOTIFY_PARTITION_EVENT,

				 input, NULL);

	local_irq_restore(irq_flags);



	if (!hv_result_success(status)) {

		hv_status_err(status, "\n");

		ret = hv_result_to_errno(status);

	}

	return ret;

}



bool hv_lp_exists(u32 lp_index)

{

	struct hv_input_get_logical_processor_run_time *input;

	struct hv_output_get_logical_processor_run_time *output;

	unsigned long flags;

	u64 status;



	local_irq_save(flags);

	input = *this_cpu_ptr(hyperv_pcpu_input_arg);

	output = *this_cpu_ptr(hyperv_pcpu_output_arg);



	input->lp_index = lp_index;

	status = hv_do_hypercall(HVCALL_GET_LOGICAL_PROCESSOR_RUN_TIME,

				 input, output);

	local_irq_restore(flags);



	if (!hv_result_success(status) &&

	    hv_result(status) != HV_STATUS_INVALID_LP_INDEX) {

		hv_status_err(status, "\n");

		BUG();

	}



	return hv_result_success(status);

}

include/asm-generic/mshyperv.h

+10 −0
Original line number Diff line number Diff line
@@ -347,6 +347,8 @@ bool hv_result_needs_memory(u64 status); 
int hv_deposit_memory_node(int node, u64 partition_id, u64 status);

int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);

int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);

int hv_call_notify_all_processors_started(void);

bool hv_lp_exists(u32 lp_index);

int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);



#else /* CONFIG_MSHV_ROOT */
@@ -366,6 +368,14 @@ static inline int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id) 
{

	return -EOPNOTSUPP;

}

static inline int hv_call_notify_all_processors_started(void)

{

	return -EOPNOTSUPP;

}

static inline bool hv_lp_exists(u32 lp_index)

{

	return false;

}

static inline int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags)

{

	return -EOPNOTSUPP;

include/hyperv/hvgdk_mini.h

+1 −0
Original line number Diff line number Diff line
@@ -435,6 +435,7 @@ union hv_vp_assist_msr_contents { /* HV_REGISTER_VP_ASSIST_PAGE */ 
/* HV_CALL_CODE */

#define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE		0x0002

#define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST		0x0003

#define HVCALL_GET_LOGICAL_PROCESSOR_RUN_TIME		0x0004

#define HVCALL_NOTIFY_LONG_SPIN_WAIT			0x0008

#define HVCALL_SEND_IPI					0x000b

#define HVCALL_ENABLE_VP_VTL				0x000f

include/hyperv/hvhdk_mini.h

+12 −0
Original line number Diff line number Diff line
@@ -362,6 +362,7 @@ union hv_partition_event_input { 


enum hv_partition_event {

	HV_PARTITION_EVENT_ROOT_CRASHDUMP = 2,

	HV_PARTITION_ALL_LOGICAL_PROCESSORS_STARTED = 4,

};



struct hv_input_notify_partition_event {
@@ -369,6 +370,17 @@ struct hv_input_notify_partition_event { 
	union hv_partition_event_input input;

} __packed;



struct hv_input_get_logical_processor_run_time {

	u32 lp_index;

} __packed;



struct hv_output_get_logical_processor_run_time {

	u64 global_time;

	u64 local_run_time;

	u64 rsvdz0;

	u64 hypervisor_time;

} __packed;



struct hv_lp_startup_status {

	u64 hv_status;

	u64 substatus1;