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Date: Mon, 17 Mar 2014 10:55:28 +0100 From: Vegard Nossum <vegard.nossum@...cle.com> To: Michal Hocko <mhocko@...e.cz>, Xishi Qiu <qiuxishi@...wei.com> CC: Andrew Morton <akpm@...ux-foundation.org>, Pekka Enberg <penberg@...nel.org>, Peter Zijlstra <peterz@...radead.org>, David Rientjes <rientjes@...gle.com>, Vegard Nossum <vegard.nossum@...il.com>, Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Li Zefan <lizefan@...wei.com> Subject: Re: kmemcheck: OS boot failed because NMI handlers access the memory tracked by kmemcheck 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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