Re: [PATCH v3 x86 1/2] fix page faults by nmiaction in nmi if kmemcheck is enabled

Don Zickus
2012-03-06T15:01:08Z

On Tue, Mar 06, 2012 at 06:09:43PM +0800, Li Zhong wrote:
> This patch tries to fix the problem of page fault exception caused by
> accessing nmiaction structure in nmi if kmemcheck is enabled.
>
> If kmemcheck is enabled, the memory allocated through slab are in pages
> that are marked non-present, so that some checks could be done in the
> page fault handling code ( e.g. whether the memory is read before
> written to ).
> As nmiaction is allocated in this way, so it resides in a non-present
> page. Then there is a page fault while the nmi code accessing the
> nmiaction structure, which would then cause a warning by
> WARN_ON_ONCE(in_nmi()) in kmemcheck_fault(), called by do_page_fault().
>
> v2: as Peter suggested, changed the nmiaction to use static storage.
>
> v3: as Peter suggested, use macro to shorten the codes. Also keep the
> original usage of register_nmi_handler, so users of this call doesn't
> need change.

Thanks Li! Looks fine to me. I'll run some tests to make sure things
still work correctly.

Cheers,
Don