RE: [PATCH 1/1] Drivers: hv: vmbus: Fix crash handler reset of Hyper-V synic

[Dexuan Cui <decui@microsoft.com>]

> From: Michael Kelley <mikelley@microsoft.com>
> Sent: Wednesday, November 13, 2019 10:32 PM
> To: linux-kernel@vger.kernel.org; vkuznets <vkuznets@redhat.com>; KY
> Srinivasan <kys@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; sashal@kernel.org; Dexuan Cui
> <decui@microsoft.com>; linux-hyperv@vger.kernel.org
> Cc: Michael Kelley <mikelley@microsoft.com>
> Subject: [PATCH 1/1] Drivers: hv: vmbus: Fix crash handler reset of Hyper-V
> synic
> 
> 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.
> 
> 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: Dexuan Cui <decui@microsoft.com>