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>

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index c506c7b80f7cb394bfa1c5d67e855ef471a4e3d5..810746d8b3bc6016b0512969d1b65057b052a28c 100644 (file)
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -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;

diff --git a/drivers/hv/hv_proc.c b/drivers/hv/hv_proc.c
index 3cb4b2a3035cfb33bafec7c1f9be91b5428b4ccb..57b2c64197cb987db45b140d92243eb06760032c 100644 (file)
--- a/drivers/hv/hv_proc.c
+++ b/drivers/hv/hv_proc.c
@@ -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);
+}

diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index d37b68238c978dd998fd9a8163e307a87c9f3466..bf601d67cecb9f199727952ae967f7f7da400ff2 100644 (file)
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -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;

diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index f9600f87186ac8828f607a2dd0e6cf9edce2975d..6a4e8b9d570fddd4d197ae79af4cd85de9c31055 100644 (file)
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -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

diff --git a/include/hyperv/hvhdk_mini.h b/include/hyperv/hvhdk_mini.h
index 091c03e26046d8bbd2fbc4ff35f9d0610f756e7b..b4cb2fa26e9bc2c0a2da4c6e15db61726cca68a8 100644 (file)
--- a/include/hyperv/hvhdk_mini.h
+++ b/include/hyperv/hvhdk_mini.h
@@ -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;