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| author | Andrea Parri (Microsoft) <parri.andrea@gmail.com> | 2020-04-06 02:15:04 +0200 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2020-04-23 13:17:11 +0000 |
| commit | 8a857c55420f29da4fc131adc22b12d474c48f4c (patch) | |
| tree | 58e1630f0c8bf8e5d9faef06ae627339ce0c3199 /drivers/hv/hv.c | |
| parent | 52c7803f9bd4b1f0ac6e2e3e6051415198cc06bd (diff) | |
| download | linux-8a857c55420f29da4fc131adc22b12d474c48f4c.tar.bz2 | |
Drivers: hv: vmbus: Always handle the VMBus messages on CPU0
A Linux guest have to pick a "connect CPU" to communicate with the
Hyper-V host. This CPU can not be taken offline because Hyper-V does
not provide a way to change that CPU assignment.
Current code sets the connect CPU to whatever CPU ends up running the
function vmbus_negotiate_version(), and this will generate problems if
that CPU is taken offine.
Establish CPU0 as the connect CPU, and add logics to prevents the
connect CPU from being taken offline. We could pick some other CPU,
and we could pick that "other CPU" dynamically if there was a reason to
do so at some point in the future. But for now, #defining the connect
CPU to 0 is the most straightforward and least complex solution.
While on this, add inline comments explaining "why" offer and rescind
messages should not be handled by a same serialized work queue.
Suggested-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20200406001514.19876-2-parri.andrea@gmail.com
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'drivers/hv/hv.c')
| -rw-r--r-- | drivers/hv/hv.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c index 6098e0cbdb4b..e2b331045464 100644 --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -250,6 +250,13 @@ int hv_synic_cleanup(unsigned int cpu) unsigned long flags; /* + * 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. + */ + if (cpu == VMBUS_CONNECT_CPU) + return -EBUSY; + + /* * Search for channels which are bound to the CPU we're about to * cleanup. In case we find one and vmbus is still connected we need to * fail, this will effectively prevent CPU offlining. There is no way |