[PATCH V4] powerpc/85xx: Add machine check handler to fix PCIe erratum on mpc85xx

[Jia Hongtao-B38951]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Thursday, March 14, 2013 12:38 AM
> To: David Laight
> Cc: Jia Hongtao-B38951; Wood Scott-B07421; linuxppc-dev at lists.ozlabs.org;
> Stuart Yoder
> Subject: Re: [PATCH V4] powerpc/85xx: Add machine check handler to fix
> PCIe erratum on mpc85xx
> 
> On 03/13/2013 04:40:40 AM, David Laight wrote:
> > > Hmm, seems there's no probe_user_address() -- for userspace we
> > > basically want the same thing minus the KERNEL_DS.  See
> > > arch/powerpc/perf/callchain.c for an example.
> >
> > Isn't that just copy_from_user() ?
> 
> Plus pagefault_disable/enable().
> 
> -Scott

pagefault_disable() is identical to preempt_disable(). So I think this
could not avoid other cpu to swap out the instruction we want to read back.
probe_kernel_address() also have the same issue.

Does this mean we can't just use pagefault_disable() to prevent from getting
the wrong instruction?

-Hongtao.