Re: [RFC] x86_64: A real proposal for iret-less return to kernel

[Andy Lutomirski]

On Wed, May 21, 2014 at 3:48 PM, Borislav Petkov <bp@xxxxxxxxx> wrote:
> On Wed, May 21, 2014 at 03:39:11PM -0700, Andy Lutomirski wrote:
>> But if we get a new MCE in here, it will be an MCE from kernel context
>> and it's fatal. So, yes, we'll clobber the stack, but we'll never
>> return (unless tolerant is set to something insane), so who cares?
>
> Ok, but we still have to do the work before returning to the process. So
> if not mce_notify_process() how else are you suggesting we do this?

I'm suggesting that you re-enable interrupts and do the work in
do_machine_check.  I think it'll just work.  It might pay to set a
flag so that you panic very loudly if do_machine_check recurses.

I suspect that, if the hardware is generating machine checks while
doing memory poisoning, the hardware is broken enough that even
panicking might not work, though :)

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/