From: Tianyu Lan Tianyu.Lan@microsoft.com
commit 74347a99e73ae00b8385f1209aaea193c670f901 upstream.
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 mikelley@microsoft.com Signed-off-by: Tianyu Lan Tianyu.Lan@microsoft.com Link: https://lore.kernel.org/r/20200406155331.2105-2-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu wei.liu@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/hv/channel_mgmt.c | 3 +++ drivers/hv/vmbus_drv.c | 21 +++++++++++++-------- 2 files changed, 16 insertions(+), 8 deletions(-)
--- 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; --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -53,9 +53,12 @@ static int hyperv_panic_event(struct not { 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; }
@@ -1389,10 +1392,16 @@ 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; @@ -2202,8 +2211,6 @@ static int vmbus_bus_suspend(struct devi
vmbus_initiate_unload(false);
- vmbus_connection.conn_state = DISCONNECTED; - /* Reset the event for the next resume. */ reinit_completion(&vmbus_connection.ready_for_resume_event);
@@ -2288,7 +2295,6 @@ 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); @@ -2305,7 +2311,6 @@ static void hv_crash_handler(struct pt_r * 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);