path: root/drivers/hv
diff options
authorChris Co <>2020-11-10 19:01:18 +0000
committerWei Liu <>2020-11-11 10:58:09 +0000
commit92e4dc8b05663d6539b1b8375f3b1cf7b204cfe9 (patch)
tree8778ca9385173a90f1994713a044473fccace400 /drivers/hv
parentdbf563eee0b8cc056744514d91c5ffc2fa6c0982 (diff)
Drivers: hv: vmbus: Allow cleanup of VMBUS_CONNECT_CPU if disconnected
When invoking kexec() on a Linux guest running on a Hyper-V host, the kernel panics. RIP: 0010:cpuhp_issue_call+0x137/0x140 Call Trace: __cpuhp_remove_state_cpuslocked+0x99/0x100 __cpuhp_remove_state+0x1c/0x30 hv_kexec_handler+0x23/0x30 [hv_vmbus] hv_machine_shutdown+0x1e/0x30 machine_shutdown+0x10/0x20 kernel_kexec+0x6d/0x96 __do_sys_reboot+0x1ef/0x230 __x64_sys_reboot+0x1d/0x20 do_syscall_64+0x6b/0x3d8 entry_SYSCALL_64_after_hwframe+0x44/0xa9 This was due to hv_synic_cleanup() callback returning -EBUSY to cpuhp_issue_call() when tearing down the VMBUS_CONNECT_CPU, even if the vmbus_connection.conn_state = DISCONNECTED. hv_synic_cleanup() should succeed in the case where vmbus_connection.conn_state is DISCONNECTED. Fix is to add an extra condition to test for vmbus_connection.conn_state == CONNECTED on the VMBUS_CONNECT_CPU and only return early if true. This way the kexec() path can still shut everything down while preserving the initial behavior of preventing CPU offlining on the VMBUS_CONNECT_CPU while the VM is running. Fixes: 8a857c55420f29 ("Drivers: hv: vmbus: Always handle the VMBus messages on CPU0") Signed-off-by: Chris Co <> Reviewed-by: Andrea Parri (Microsoft) <> Cc: Link: Signed-off-by: Wei Liu <>
Diffstat (limited to 'drivers/hv')
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index da69338f92f5..75a8638ff68b 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -244,9 +244,13 @@ int hv_synic_cleanup(unsigned int cpu)
* Hyper-V does not provide a way to change the connect CPU once
- * it is set; we must prevent the connect CPU from going offline.
+ * it is set; we must prevent the connect CPU from going offline
+ * while the VM is running normally. But in the panic or kexec()
+ * path where the vmbus is already disconnected, the CPU must be
+ * allowed to shut down.
- if (cpu == VMBUS_CONNECT_CPU)
+ if (cpu == VMBUS_CONNECT_CPU &&
+ vmbus_connection.conn_state == CONNECTED)
return -EBUSY;