Re: [PATCH 1/1] Drivers: hv: vmbus: Fix crash handler reset of Hyper-V synic
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: 2019-11-14 10:04:23
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lkml
Michael Kelley [off-list ref] 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().
quoted hunk ↗ jump to hunk
Signed-off-by: Michael Kelley <redacted> --- 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