From 032d4a4802209fe25ce44deb2c002dccf663925f Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 19 Mar 2020 16:32:26 -0500 Subject: [PATCH 1/9] hv: hyperv_vmbus.h: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Wei Liu --- drivers/hv/hyperv_vmbus.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h index f5fa3b3c9baf76..70b30e223a578b 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -292,7 +292,7 @@ struct vmbus_msginfo { struct list_head msglist_entry; /* The message itself */ - unsigned char msg[0]; + unsigned char msg[]; }; From 3e0d3776501a215358e3d91045b74f35a7eeaad9 Mon Sep 17 00:00:00 2001 From: YueHaibing Date: Fri, 3 Apr 2020 16:28:45 +0800 Subject: [PATCH 2/9] hv_debugfs: Make hv_debug_root static Fix sparse warning: drivers/hv/hv_debugfs.c:14:15: warning: symbol 'hv_debug_root' was not declared. Should it be static? Reported-by: Hulk Robot Signed-off-by: YueHaibing Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200403082845.22740-1-yuehaibing@huawei.com Signed-off-by: Wei Liu --- drivers/hv/hv_debugfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/hv/hv_debugfs.c b/drivers/hv/hv_debugfs.c index 8a28785735820b..ccf752b6659a77 100644 --- a/drivers/hv/hv_debugfs.c +++ b/drivers/hv/hv_debugfs.c @@ -11,7 +11,7 @@ #include "hyperv_vmbus.h" -struct dentry *hv_debug_root; +static struct dentry *hv_debug_root; static int hv_debugfs_delay_get(void *data, u64 *val) { From 97d9f1c43bedd400301d6f1eff54d46e8c636e47 Mon Sep 17 00:00:00 2001 From: Olaf Hering Date: Tue, 7 Apr 2020 19:27:39 +0200 Subject: [PATCH 3/9] x86: hyperv: report value of misc_features A few kernel features depend on ms_hyperv.misc_features, but unlike its siblings ->features and ->hints, the value was never reported during boot. Signed-off-by: Olaf Hering Link: https://lore.kernel.org/r/20200407172739.31371-1-olaf@aepfle.de Signed-off-by: Wei Liu --- arch/x86/kernel/cpu/mshyperv.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index caa032ce3fe311..53706fb564337c 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -227,8 +227,8 @@ static void __init ms_hyperv_init_platform(void) ms_hyperv.misc_features = cpuid_edx(HYPERV_CPUID_FEATURES); ms_hyperv.hints = cpuid_eax(HYPERV_CPUID_ENLIGHTMENT_INFO); - pr_info("Hyper-V: features 0x%x, hints 0x%x\n", - ms_hyperv.features, ms_hyperv.hints); + pr_info("Hyper-V: features 0x%x, hints 0x%x, misc 0x%x\n", + ms_hyperv.features, ms_hyperv.hints, ms_hyperv.misc_features); ms_hyperv.max_vp_index = cpuid_eax(HYPERV_CPUID_IMPLEMENT_LIMITS); ms_hyperv.max_lp_index = cpuid_ebx(HYPERV_CPUID_IMPLEMENT_LIMITS); From 74347a99e73ae00b8385f1209aaea193c670f901 Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:26 -0700 Subject: [PATCH 4/9] x86/Hyper-V: Unload vmbus channel in hv panic callback When kdump is not configured, a Hyper-V VM might still respond to network traffic after a kernel panic when kernel parameter panic=0. The panic CPU goes into an infinite loop with interrupts enabled, and the VMbus driver interrupt handler still works because the VMbus connection is unloaded only in the kdump path. The network responses make the other end of the connection think the VM is still functional even though it has panic'ed, which could affect any failover actions that should be taken. Fix this by unloading the VMbus connection during the panic process. vmbus_initiate_unload() could then be called twice (e.g., by hyperv_panic_event() and hv_crash_handler(), so reset the connection state in vmbus_initiate_unload() to ensure the unload is done only once. Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-2-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- drivers/hv/channel_mgmt.c | 3 +++ drivers/hv/vmbus_drv.c | 21 +++++++++++++-------- 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 0370364169c4ec..501c43c5851dcc 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -839,6 +839,9 @@ void vmbus_initiate_unload(bool crash) { struct vmbus_channel_message_header hdr; + if (xchg(&vmbus_connection.conn_state, DISCONNECTED) == DISCONNECTED) + return; + /* Pre-Win2012R2 hosts don't support reconnect */ if (vmbus_proto_version < VERSION_WIN8_1) return; diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 029378c27421d1..6478240d11ab46 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -53,9 +53,12 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val, { struct pt_regs *regs; - regs = current_pt_regs(); + vmbus_initiate_unload(true); - hyperv_report_panic(regs, val); + if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) { + regs = current_pt_regs(); + hyperv_report_panic(regs, val); + } return NOTIFY_DONE; } @@ -1391,10 +1394,16 @@ static int vmbus_bus_init(void) } register_die_notifier(&hyperv_die_block); - atomic_notifier_chain_register(&panic_notifier_list, - &hyperv_panic_block); } + /* + * Always register the panic notifier because we need to unload + * the VMbus channel connection to prevent any VMbus + * activity after the VM panics. + */ + atomic_notifier_chain_register(&panic_notifier_list, + &hyperv_panic_block); + vmbus_request_offers(); return 0; @@ -2204,8 +2213,6 @@ static int vmbus_bus_suspend(struct device *dev) vmbus_initiate_unload(false); - vmbus_connection.conn_state = DISCONNECTED; - /* Reset the event for the next resume. */ reinit_completion(&vmbus_connection.ready_for_resume_event); @@ -2289,7 +2296,6 @@ static void hv_kexec_handler(void) { hv_stimer_global_cleanup(); vmbus_initiate_unload(false); - vmbus_connection.conn_state = DISCONNECTED; /* Make sure conn_state is set as hv_synic_cleanup checks for it */ mb(); cpuhp_remove_state(hyperv_cpuhp_online); @@ -2306,7 +2312,6 @@ static void hv_crash_handler(struct pt_regs *regs) * doing the cleanup for current CPU only. This should be sufficient * for kdump. */ - vmbus_connection.conn_state = DISCONNECTED; cpu = smp_processor_id(); hv_stimer_cleanup(cpu); hv_synic_disable_regs(cpu); From 7f11a2cc10a4ae3a70e2c73361f4a9a33503539b Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:27 -0700 Subject: [PATCH 5/9] x86/Hyper-V: Free hv_panic_page when fail to register kmsg dump If kmsg_dump_register() fails, hv_panic_page will not be used anywhere. So free and reset it. Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-3-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- drivers/hv/vmbus_drv.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 6478240d11ab46..00a511f1592646 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1385,9 +1385,13 @@ static int vmbus_bus_init(void) hv_panic_page = (void *)hv_alloc_hyperv_zeroed_page(); if (hv_panic_page) { ret = kmsg_dump_register(&hv_kmsg_dumper); - if (ret) + if (ret) { pr_err("Hyper-V: kmsg dump register " "error 0x%x\n", ret); + hv_free_hyperv_page( + (unsigned long)hv_panic_page); + hv_panic_page = NULL; + } } else pr_err("Hyper-V: panic message page memory " "allocation failed"); @@ -1416,7 +1420,6 @@ static int vmbus_bus_init(void) hv_remove_vmbus_irq(); bus_unregister(&hv_bus); - hv_free_hyperv_page((unsigned long)hv_panic_page); unregister_sysctl_table(hv_ctl_table_hdr); hv_ctl_table_hdr = NULL; return ret; From 73f26e526f19afb3a06b76b970a76bcac2cafd05 Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:28 -0700 Subject: [PATCH 6/9] x86/Hyper-V: Trigger crash enlightenment only once during system crash. When a guest VM panics, Hyper-V should be notified only once via the crash synthetic MSRs. Current Linux code might write these crash MSRs twice during a system panic: 1) hyperv_panic/die_event() calling hyperv_report_panic() 2) hv_kmsg_dump() calling hyperv_report_panic_msg() Fix this by not calling hyperv_report_panic() if a kmsg dump has been successfully registered. The notification will happen later via hyperv_report_panic_msg(). Fixes: 7ed4325a44ea ("Drivers: hv: vmbus: Make panic reporting to be more useful") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-4-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- drivers/hv/vmbus_drv.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 00a511f1592646..333dad39b1c167 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -55,7 +55,13 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val, vmbus_initiate_unload(true); - if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) { + /* + * Hyper-V should be notified only once about a panic. If we will be + * doing hyperv_report_panic_msg() later with kmsg data, don't do + * the notification here. + */ + if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE + && !hv_panic_page) { regs = current_pt_regs(); hyperv_report_panic(regs, val); } @@ -68,7 +74,13 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val, struct die_args *die = (struct die_args *)args; struct pt_regs *regs = die->regs; - hyperv_report_panic(regs, val); + /* + * Hyper-V should be notified only once about a panic. If we will be + * doing hyperv_report_panic_msg() later with kmsg data, don't do + * the notification here. + */ + if (!hv_panic_page) + hyperv_report_panic(regs, val); return NOTIFY_DONE; } From a11589563e96bf262767294b89b25a9d44e7303b Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:29 -0700 Subject: [PATCH 7/9] x86/Hyper-V: Report crash register data or kmsg before running crash kernel We want to notify Hyper-V when a Linux guest VM crash occurs, so there is a record of the crash even when kdump is enabled. But crash_kexec_post_notifiers defaults to "false", so the kdump kernel runs before the notifiers and Hyper-V never gets notified. Fix this by always setting crash_kexec_post_notifiers to be true for Hyper-V VMs. Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-5-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- arch/x86/kernel/cpu/mshyperv.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 53706fb564337c..ebf34c7bc8bc0d 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -263,6 +263,16 @@ static void __init ms_hyperv_init_platform(void) cpuid_eax(HYPERV_CPUID_NESTED_FEATURES); } + /* + * Hyper-V expects to get crash register data or kmsg when + * crash enlightment is available and system crashes. Set + * crash_kexec_post_notifiers to be true to make sure that + * calling crash enlightment interface before running kdump + * kernel. + */ + if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) + crash_kexec_post_notifiers = true; + #ifdef CONFIG_X86_LOCAL_APIC if (ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS && ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) { From 040026df7088c56ccbad28f7042308f67bde63df Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:30 -0700 Subject: [PATCH 8/9] x86/Hyper-V: Report crash register data when sysctl_record_panic_msg is not set When sysctl_record_panic_msg is not set, the panic will not be reported to Hyper-V via hyperv_report_panic_msg(). So the crash should be reported via hyperv_report_panic(). Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley Signed-off-by: Tianyu Lan Link: https://lore.kernel.org/r/20200406155331.2105-6-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- drivers/hv/vmbus_drv.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 333dad39b1c167..172ceae69abb7e 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -48,6 +48,18 @@ static int hyperv_cpuhp_online; static void *hv_panic_page; +/* + * 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; + +static int hyperv_report_reg(void) +{ + return !sysctl_record_panic_msg || !hv_panic_page; +} + static int hyperv_panic_event(struct notifier_block *nb, unsigned long val, void *args) { @@ -61,7 +73,7 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val, * the notification here. */ if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE - && !hv_panic_page) { + && hyperv_report_reg()) { regs = current_pt_regs(); hyperv_report_panic(regs, val); } @@ -79,7 +91,7 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val, * doing hyperv_report_panic_msg() later with kmsg data, don't do * the notification here. */ - if (!hv_panic_page) + if (hyperv_report_reg()) hyperv_report_panic(regs, val); return NOTIFY_DONE; } @@ -1267,13 +1279,6 @@ 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. From f3a99e761efa616028b255b4de58e9b5b87c5545 Mon Sep 17 00:00:00 2001 From: Tianyu Lan Date: Mon, 6 Apr 2020 08:53:31 -0700 Subject: [PATCH 9/9] x86/Hyper-V: Report crash data in die() when panic_on_oops is set When oops happens with panic_on_oops unset, the oops thread is killed by die() and system continues to run. In such case, guest should not report crash register data to host since system still runs. Check panic_on_oops and return directly in hyperv_report_panic() when the function is called in the die() and panic_on_oops is unset. Fix it. Fixes: 7ed4325a44ea ("Drivers: hv: vmbus: Make panic reporting to be more useful") Signed-off-by: Tianyu Lan Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200406155331.2105-7-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu --- arch/x86/hyperv/hv_init.c | 6 +++++- drivers/hv/vmbus_drv.c | 5 +++-- include/asm-generic/mshyperv.h | 2 +- 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index b0da5320bcff84..624f5d9b0f79f9 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -419,11 +420,14 @@ void hyperv_cleanup(void) } EXPORT_SYMBOL_GPL(hyperv_cleanup); -void hyperv_report_panic(struct pt_regs *regs, long err) +void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die) { static bool panic_reported; u64 guest_id; + if (in_die && !panic_on_oops) + return; + /* * We prefer to report panic on 'die' chain as we have proper * registers to report, but if we miss it (e.g. on BUG()) we need diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 172ceae69abb7e..a68bce4d0ddbe9 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include #include "hyperv_vmbus.h" @@ -75,7 +76,7 @@ static int hyperv_panic_event(struct notifier_block *nb, unsigned long val, if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE && hyperv_report_reg()) { regs = current_pt_regs(); - hyperv_report_panic(regs, val); + hyperv_report_panic(regs, val, false); } return NOTIFY_DONE; } @@ -92,7 +93,7 @@ static int hyperv_die_event(struct notifier_block *nb, unsigned long val, * the notification here. */ if (hyperv_report_reg()) - hyperv_report_panic(regs, val); + hyperv_report_panic(regs, val, true); return NOTIFY_DONE; } diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h index b3f1082cc435c8..1c4fd950f09123 100644 --- a/include/asm-generic/mshyperv.h +++ b/include/asm-generic/mshyperv.h @@ -163,7 +163,7 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset, return nr_bank; } -void hyperv_report_panic(struct pt_regs *regs, long err); +void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die); void hyperv_report_panic_msg(phys_addr_t pa, size_t size); bool hv_is_hyperv_initialized(void); bool hv_is_hibernation_supported(void);