On 03/05/2013 04:12:30 AM, Jia Hongtao-B38951 wrote:

=20
=20

quoted

-----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 =20

fix

quoted

PCIe erratum on mpc85xx

On 03/04/2013 10:16:10 AM, Stuart Yoder wrote:

quoted

On Mon, Mar 4, 2013 at 2:40 AM, Jia Hongtao [off-list ref]
wrote:

quoted

A PCIe erratum of mpc85xx may causes a core hang when a link of =20

PCIe

quoted

quoted

quoted

goes down. when the link goes down, Non-posted transactions =20

issued

quoted

quoted

quoted

via the ATMU requiring completion result in an instruction =20

stall.

quoted

quoted

quoted

At the same time a machine-check exception is generated to the =20

core

quoted

quoted

quoted

to allow further processing by the handler. We implements the

handler

quoted

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 =20

nothing is

quoted

quoted

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.

=20
You discuss this with Liu Shuo about a year ago.
here is the log:
=20
"
On 02/01/2012 02:18 AM, shuo.liu@freescale.com wrote:

quoted

v3 : Skip the instruction only. Don't access the user space memory =20

in

quoted

     mechine check.

=20
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 =20
(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 =20
the "for now". :-)

-Scott=