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SubjectRe: [PATCH 1/1] Drivers: hv: vmbus: Fix crash handler reset of Hyper-V synic
Date
Michael Kelley <mikelley@microsoft.com> writes:

> The crash handler calls hv_synic_cleanup() to shutdown the
> Hyper-V synthetic interrupt controller. But if the CPU
> that calls hv_synic_cleanup() has a VMbus channel interrupt
> assigned to it (which is likely the case in smaller VM sizes),
> hv_synic_cleanup() returns an error and the synthetic
> interrupt controller isn't shutdown. While the lack of
> being shutdown hasn't caused a known problem, it still
> should be fixed for highest reliability.
>
> So directly call hv_synic_disable_regs() instead of
> hv_synic_cleanup(), which ensures that the synic is always
> shutdown.

Generally, when performing kdump doing as little work as possible is
always preferred and hv_synic_cleanup() does too much: taking mutex,
walking through channel list,...

Also, hv_synic_cleanup() was calling hv_stimer_cleanup() and we have a
second redundant invocation in hv_crash_handler().

>
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
> drivers/hv/vmbus_drv.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 664a415..665920d 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2305,7 +2305,7 @@ static void hv_crash_handler(struct pt_regs *regs)
> vmbus_connection.conn_state = DISCONNECTED;
> cpu = smp_processor_id();
> hv_stimer_cleanup(cpu);
> - hv_synic_cleanup(cpu);
> + hv_synic_disable_regs(cpu);
> hyperv_cleanup();
> };

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly

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