When the kernel panics, one page worth of kmsg data is written to an allocated page. The Hypervisor is notified of the page address trough the MSR. This panic information is collected on the host. Since we are only collecting one page of data, the full panic message may not be collected. Each line of the panic message is prefixed with the log level of that particular message in the form <N>, where N is the log level. The typical 4 Kbytes contains anywhere from 50 to 100 lines with that log level prefix. hv_dmsg_dump() makes a call to kmsg_dump_get_buffer(). The second argument in the call is a bool described as: ‘@syslog: include the “<4>” Prefixes’. With this change, we will not write the log level to the allocated page. This will provide additional room in the allocated page for more informative panic information. Requesting in stable kernels, since many kernels running in production are stable releases. Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx> --- 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 9147ee9d5f7d..d69f4efa3719 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1368,7 +1368,7 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper, * Write dump contents to the page. No need to synchronize; panic should * be single-threaded. */ - kmsg_dump_get_buffer(dumper, true, hv_panic_page, HV_HYP_PAGE_SIZE, + kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE, &bytes_written); if (bytes_written) hyperv_report_panic_msg(panic_pa, bytes_written); -- 2.17.1
