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

[Jiri Kosina]

On Wed, 21 May 2014, Borislav Petkov wrote:

> > ISTM the do_machine_check code ought to consider any kill-worthy MCE
> > from kernel space to be non-recoverable, but I want to keep the scope
> > of these patches under control.
> 
> MCA has a bit called RIPV which, if set, signals that RIP is valid and
> it is safe to return provided we've taken proper care of handling even
> non-correctable errors (memory poisoning, etc).

Yeah, but it tries to send SIGBUS from MCE context. And if MCE triggered 
at the time the CPU was already holding sighand->siglock for that 
particular task, it'll deadlock against itself.

-- 
Jiri Kosina
SUSE Labs
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