@@ -38,6 +38,7 @@ show up in /proc/sys/kernel:
- hung_task_check_count
- hung_task_timeout_secs
- hung_task_warnings
+- hyperv_record_panic_msg
- kexec_load_disabled
- kptr_restrict
- l2cr [ PPC only ]
@@ -360,6 +361,16 @@ This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
==============================================================
+hyperv_record_panic_msg:
+
+Controls whether the panic kmsg data should be reported to Hyper-V.
+
+0: do not report panic kmsg data.
+
+1: report the panic kmsg data. This is the default behavior.
+
+==============================================================
+
kexec_load_disabled:
A toggle indicating if the kexec_load syscall has been disabled. This
@@ -459,6 +459,33 @@ void hyperv_report_panic(struct pt_regs *regs, long err)
}
EXPORT_SYMBOL_GPL(hyperv_report_panic);
+/**
+ * hyperv_report_panic_msg - report panic message to Hyper-V
+ * @pa: physical address of the panic page containing the message
+ * @size: size of the message in the page
+ */
+void hyperv_report_panic_msg(phys_addr_t pa, size_t size)
+{
+ /*
+ * P3 to contain the physical address of the panic page & P4 to
+ * contain the size of the panic data in that page. Rest of the
+ * registers are no-op when the NOTIFY_MSG flag is set.
+ */
+ wrmsrl(HV_X64_MSR_CRASH_P0, 0);
+ wrmsrl(HV_X64_MSR_CRASH_P1, 0);
+ wrmsrl(HV_X64_MSR_CRASH_P2, 0);
+ wrmsrl(HV_X64_MSR_CRASH_P3, pa);
+ wrmsrl(HV_X64_MSR_CRASH_P4, size);
+
+ /*
+ * Let Hyper-V know there is crash data available along with
+ * the panic message.
+ */
+ wrmsrl(HV_X64_MSR_CRASH_CTL,
+ (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
+}
+EXPORT_SYMBOL_GPL(hyperv_report_panic_msg);
+
bool hv_is_hyperv_initialized(void)
{
union hv_x64_msr_hypercall_contents hypercall_msr;
@@ -172,9 +172,10 @@
#define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED (1 << 14)
/*
- * Crash notification flag.
+ * Crash notification flags.
*/
-#define HV_CRASH_CTL_CRASH_NOTIFY (1ULL << 63)
+#define HV_CRASH_CTL_CRASH_NOTIFY_MSG BIT_ULL(62)
+#define HV_CRASH_CTL_CRASH_NOTIFY BIT_ULL(63)
/* MSR used to identify the guest OS. */
#define HV_X64_MSR_GUEST_OS_ID 0x40000000
@@ -285,6 +285,7 @@ void __init hyperv_init(void);
void hyperv_setup_mmu_ops(void);
void hyper_alloc_mmu(void);
void hyperv_report_panic(struct pt_regs *regs, long err);
+void hyperv_report_panic_msg(phys_addr_t pa, size_t size);
bool hv_is_hyperv_initialized(void);
void hyperv_cleanup(void);
@@ -56,6 +56,8 @@ static struct completion probe_event;
static int hyperv_cpuhp_online;
+static void *hv_panic_page;
+
static int hyperv_panic_event(struct notifier_block *nb, unsigned long val,
void *args)
{
@@ -1068,6 +1070,75 @@ static void vmbus_isr(void)
add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR, 0);
}
+/*
+ * Boolean to control whether to report panic messages over Hyper-V.
+ *
+ * It can be set via /proc/sys/kernel/hyperv/record_panic_msg
+ */
+static int sysctl_record_panic_msg = 1;
+
+/*
+ * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
+ * buffer and call into Hyper-V to transfer the data.
+ */
+static void hv_kmsg_dump(struct kmsg_dumper *dumper,
+ enum kmsg_dump_reason reason)
+{
+ size_t bytes_written;
+ phys_addr_t panic_pa;
+
+ /* We are only interested in panics. */
+ if ((reason != KMSG_DUMP_PANIC) || (!sysctl_record_panic_msg))
+ return;
+
+ panic_pa = virt_to_phys(hv_panic_page);
+
+ /*
+ * Write dump contents to the page. No need to synchronize; panic should
+ * be single-threaded.
+ */
+ if (!kmsg_dump_get_buffer(dumper, true, hv_panic_page,
+ PAGE_SIZE, &bytes_written)) {
+ pr_err("Hyper-V: Unable to get kmsg data for panic\n");
+ return;
+ }
+
+ hyperv_report_panic_msg(panic_pa, bytes_written);
+}
+
+static struct kmsg_dumper hv_kmsg_dumper = {
+ .dump = hv_kmsg_dump,
+};
+
+static struct ctl_table_header *hv_ctl_table_hdr;
+static int zero;
+static int one = 1;
+
+/*
+ * sysctl option to allow the user to control whether kmsg data should be
+ * reported to Hyper-V on panic.
+ */
+static struct ctl_table hv_ctl_table[] = {
+ {
+ .procname = "hyperv_record_panic_msg",
+ .data = &sysctl_record_panic_msg,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &one
+ },
+ {}
+};
+
+static struct ctl_table hv_root_table[] = {
+ {
+ .procname = "kernel",
+ .mode = 0555,
+ .child = hv_ctl_table
+ },
+ {}
+};
/*
* vmbus_bus_init -Main vmbus driver initialization routine.
@@ -1115,6 +1186,32 @@ static int vmbus_bus_init(void)
* Only register if the crash MSRs are available
*/
if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+ u64 hyperv_crash_ctl;
+ /*
+ * Sysctl registration is not fatal, since by default
+ * reporting is enabled.
+ */
+ hv_ctl_table_hdr = register_sysctl_table(hv_root_table);
+ if (!hv_ctl_table_hdr)
+ pr_err("Hyper-V: sysctl table register error");
+
+ /*
+ * Register for panic kmsg callback only if the right
+ * capability is supported by the hypervisor.
+ */
+ rdmsrl(HV_X64_MSR_CRASH_CTL, hyperv_crash_ctl);
+ if (hyperv_crash_ctl & HV_CRASH_CTL_CRASH_NOTIFY_MSG) {
+ hv_panic_page = (void *)get_zeroed_page(GFP_KERNEL);
+ if (hv_panic_page) {
+ ret = kmsg_dump_register(&hv_kmsg_dumper);
+ if (ret)
+ pr_err("Hyper-V: kmsg dump register "
+ "error 0x%x\n", ret);
+ } else
+ pr_err("Hyper-V: panic message page memory "
+ "allocation failed");
+ }
+
register_die_notifier(&hyperv_die_block);
atomic_notifier_chain_register(&panic_notifier_list,
&hyperv_panic_block);
@@ -1131,6 +1228,11 @@ static int vmbus_bus_init(void)
hv_remove_vmbus_irq();
bus_unregister(&hv_bus);
+ free_page((unsigned long)hv_panic_page);
+ if (!hv_ctl_table_hdr) {
+ unregister_sysctl_table(hv_ctl_table_hdr);
+ hv_ctl_table_hdr = NULL;
+ }
return ret;
}
@@ -1821,10 +1923,18 @@ static void __exit vmbus_exit(void)
vmbus_free_channels();
if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+ kmsg_dump_unregister(&hv_kmsg_dumper);
unregister_die_notifier(&hyperv_die_block);
atomic_notifier_chain_unregister(&panic_notifier_list,
&hyperv_panic_block);
}
+
+ free_page((unsigned long)hv_panic_page);
+ if (!hv_ctl_table_hdr) {
+ unregister_sysctl_table(hv_ctl_table_hdr);
+ hv_ctl_table_hdr = NULL;
+ }
+
bus_unregister(&hv_bus);
cpuhp_remove_state(hyperv_cpuhp_online);