On 03/17/2014 10:51 AM, Michal Hocko wrote:
On Mon 17-03-14 17:19:33, Xishi Qiu wrote:
OS boot failed when set cmdline kmemcheck=1. The reason is that
NMI handlers will access the memory from kmalloc(), this will cause
page fault, because memory from kmalloc() is tracked by kmemcheck.
watchdog_nmi_enable()
perf_event_create_kernel_counter()
perf_event_alloc()
event = kzalloc(sizeof(*event), GFP_KERNEL);
Where is this path called from an NMI context?
Your trace bellow points at something else and it doesn't seem to
allocate any memory either. It looks more like x86_perf_event_update
sees an invalid perf_event or something like that...
It's not important that the kzalloc() is called from NMI context, it's
important that the memory that was allocated is touched (read/written)
from NMI context.
I'm currently looking into the possibility of handling recursive faults
in kmemcheck (using the approach outlined by peterz; see
https://lkml.org/lkml/2014/2/26/141).
Vegard
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