On 03/05/2013 04:12:30 AM, Jia Hongtao-B38951 wrote:
> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Tuesday, March 05, 2013 7:46 AM
> To: Stuart Yoder
> Cc: Jia Hongtao-B38951; linuxppc-dev@lists.ozlabs.org; Kumar Gala
> Subject: Re: [PATCH V4] powerpc/85xx: Add machine check handler to
fix
> PCIe erratum on mpc85xx
>
> On 03/04/2013 10:16:10 AM, Stuart Yoder wrote:
> > On Mon, Mar 4, 2013 at 2:40 AM, Jia Hongtao <b38...@freescale.com>
> > wrote:
> > > A PCIe erratum of mpc85xx may causes a core hang when a link of
PCIe
> > > goes down. when the link goes down, Non-posted transactions
issued
> > > via the ATMU requiring completion result in an instruction
stall.
> > > At the same time a machine-check exception is generated to the
core
> > > to allow further processing by the handler. We implements the
> > handler
> > > which skips the instruction caused the stall.
> >
> > Can you explain at a high level how just skipping an instruction
> > solves
> > anything? If you just skip a load/store and continue like
nothing is
> > wrong, isn't your system possibly in a really bad state.
>
> If the instruction was a load, we probably at least want to fill the
> destination register with 0xffffffff or similar.
You discuss this with Liu Shuo about a year ago.
here is the log:
"
On 02/01/2012 02:18 AM, shuo....@freescale.com wrote:
> v3 : Skip the instruction only. Don't access the user space memory
in
> mechine check.
It may be the least bad option for now, but be aware that there's a
small chance that this will cause a leak of sensitive information
(such
as a piece of a crypto key that happened to be sitting in the register
to be loaded into).
Yes, that's (one reason) why you'd want to fill in a known value. Note
the "for now". :-)
-Scott
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