On Tue, Nov 10, 2020 at 09:18:33PM +0100, Andrea Parri wrote:
> On Tue, Nov 10, 2020 at 07:01:18PM +0000, Chris Co wrote:
> > From: Chris Co <chrco@xxxxxxxxxxxxx>
> >
> > 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 <chrco@xxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
>
> Reviewed-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
Applied to hyperv-fixes. Thanks Chris and Andrea.
Wei.
