Messages in this thread | | | Subject | Re: [PATCH 0/4] x86/Hyper-V: Unload vmbus channel in hv panic callback | From | Tianyu Lan <> | Date | Thu, 19 Mar 2020 16:24:13 +0800 |
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On 3/18/2020 1:35 AM, Wei Liu wrote: > On Tue, Mar 17, 2020 at 06:25:20AM -0700, ltykernel@gmail.com wrote: >> From: Tianyu Lan <Tianyu.Lan@microsoft.com> >> >> Customer reported Hyper-V VM still responded network traffic >> ack packets after kernel panic with kernel parameter "panic=0”. >> This becauses vmbus driver interrupt handler still works >> on the panic cpu after kernel panic. Panic cpu falls into >> infinite loop of panic() with interrupt enabled at that point. >> Vmbus driver can still handle network traffic. >> >> This confuses remote service that the panic system is still >> alive when it gets ack packets. Unload vmbus channel in hv panic >> callback and fix it. >> >> vmbus_initiate_unload() maybe double called during panic process >> (e.g, hyperv_panic_event() and hv_crash_handler()). So check >> and set connection state in vmbus_initiate_unload() to resolve >> reenter issue. >> >> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com> >> --- >> drivers/hv/channel_mgmt.c | 5 +++++ >> drivers/hv/vmbus_drv.c | 17 +++++++++-------- >> 2 files changed, 14 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c >> index 0370364169c4..893493f2b420 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 (vmbus_connection.conn_state == DISCONNECTED) >> + return; >> + >> /* Pre-Win2012R2 hosts don't support reconnect */ >> if (vmbus_proto_version < VERSION_WIN8_1) >> return; >> @@ -857,6 +860,8 @@ void vmbus_initiate_unload(bool crash) >> wait_for_completion(&vmbus_connection.unload_event); >> else >> vmbus_wait_for_unload(); >> + >> + vmbus_connection.conn_state = DISCONNECTED; > > This is only set at the end of the function. I don't see how this solve > the re-entrant issue with the check at the beginning. Do I miss anything > here? >
For this issue, vmbus_initiate_unload() maybe called on the panic vcpu twice and so just split check and set conn_state.
> Maybe this function should check and set the state to > DISCONNECTING/DISCONNECTED at the beginning of this function? > Yes, Vitaly also gave suggestion to use "xchg" to check and set conn_state. Will update in the next version.
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