> -----Original Message----- > From: Sunil Muthuswamy > Sent: Friday, June 8, 2018 11:39 AM > To: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > Cc: devel@xxxxxxxxxxxxxxxxxxxxxx; Sunil Muthuswamy > <sunilmut@xxxxxxxxxxxxx>; KY Srinivasan <kys@xxxxxxxxxxxxx>; Stephen > Hemminger <sthemmin@xxxxxxxxxxxxx> > Subject: [PATCH v5] Drivers: HV: Send one page worth of kmsg dump over > Hyper-V during panic > > In the VM mode on Hyper-V, currently, when the kernel panics, an error > code and few register values are populated in an MSR and the Hypervisor > notified. This information is collected on the host. The amount of > information currently collected is found to be limited and not very > actionable. To gather more actionable data, such as stack trace, the > proposal is to write one page worth of kmsg data on an allocated page > and the Hypervisor notified of the page address through the MSR. > > - Sysctl option to control the behavior, with ON by default. > > Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> > Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx> > Signed-off-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx> > --- > Changes since v1: > - Added a sysctl config option to allow the user to control if panic message > should be reported to Hyper-V. > > Changes since v2: > - Addressed comments from Greg KH. > - Moved the sysctl config option from 'kernel.hyperv' to 'kernel.' since the > likelihood of having many Hyper-V specific sysctl config options seemed less > and so having a specific dir for Hyper-V seemed unnecessary overhead. > > Changes since v3: > - The feature is only enabled if the capability is supported by the hypervisor. > This is done by reading the crash control MSR, in addition to the pre-existing > check for the hypervisor feature using the CPUID. > > Changes since v4: > - Addressed comments from Dexuan Cui: moved the global variable to static. > --- > Documentation/sysctl/kernel.txt | 11 ++++ > arch/x86/hyperv/hv_init.c | 27 +++++++++ > arch/x86/include/asm/hyperv-tlfs.h | 5 +- > arch/x86/include/asm/mshyperv.h | 1 + > drivers/hv/vmbus_drv.c | 116 > +++++++++++++++++++++++++++++++++++++ > 5 files changed, 158 insertions(+), 2 deletions(-) > > diff --git a/Documentation/sysctl/kernel.txt > b/Documentation/sysctl/kernel.txt > index eded671d..5958503 100644 > --- a/Documentation/sysctl/kernel.txt > +++ b/Documentation/sysctl/kernel.txt > @@ -39,6 +39,7 @@ 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 ] > @@ -374,6 +375,16 @@ 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 > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > index cfecc22..af57162 100644 > --- a/arch/x86/hyperv/hv_init.c > +++ b/arch/x86/hyperv/hv_init.c > @@ -395,6 +395,33 @@ 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; > diff --git a/arch/x86/include/asm/hyperv-tlfs.h > b/arch/x86/include/asm/hyperv-tlfs.h > index 416cb0e..76c58af 100644 > --- a/arch/x86/include/asm/hyperv-tlfs.h > +++ b/arch/x86/include/asm/hyperv-tlfs.h > @@ -171,9 +171,10 @@ > #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 > diff --git a/arch/x86/include/asm/mshyperv.h > b/arch/x86/include/asm/mshyperv.h > index b90e796..ac83f2d 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -262,6 +262,7 @@ void 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); > > diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c > index b10fe26..eec3b235 100644 > --- a/drivers/hv/vmbus_drv.c > +++ b/drivers/hv/vmbus_drv.c > @@ -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) > { > @@ -1018,6 +1020,75 @@ 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. > @@ -1065,6 +1136,38 @@ 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; > + if (!hv_ctl_table_hdr) { When vmus_bus_init is invoked, would hv_ctl_table_hdr ever be Non-NULL? > + /* > + * Sysctl registration is not fatal, since default is > + * for operation. > + */ > + 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) { Why is this allocation failure fatal in terms failing the load of the driver? If we failed to allocate why can't we revert to the existing panic notification scheme. > + ret = -ENOMEM; > + goto err_connect; > + } > + > + ret = kmsg_dump_register(&hv_kmsg_dumper); > + if (ret) { > + pr_err("Hyper-V: kmsg dump register error " > + "0x%x\n", ret); > + goto err_connect; > + } > + } > + > register_die_notifier(&hyperv_die_block); > atomic_notifier_chain_register(&panic_notifier_list, > &hyperv_panic_block); > @@ -1081,6 +1184,11 @@ 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; > } > @@ -1785,10 +1893,18 @@ 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); > -- > 2.7.4 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel