Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 31 Dec 2018 12:08:15 -0800 | Subject | Re: [RFC v2 1/6] x86: introduce kernel restartable sequence |
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On Sun, Dec 30, 2018 at 11:20 PM Nadav Amit <namit@vmware.com> wrote: > > It is sometimes beneficial to have a restartable sequence - very few > instructions which if they are preempted jump to a predefined point. > > To provide such functionality on x86-64, we use an empty REX-prefix > (opcode 0x40) as an indication for instruction in such a sequence. Before > calling the schedule IRQ routine, if the "magic" prefix is found, we > call a routine to adjust the instruction pointer. It is expected that > this opcode is not in common use. > > The following patch will make use of this function. Since there are no > other users (yet?), the patch does not bother to create a general > infrastructure and API that others can use for such sequences. Yet, it > should not be hard to make such extension later.
The following patch does not use it. Can you update this?
> +asmlinkage __visible void restart_kernel_rseq(struct pt_regs *regs) > +{ > + if (user_mode(regs) || *(u8 *)regs->ip != KERNEL_RESTARTABLE_PREFIX) > + return;
else?
I suspect something is missing here. Or I'm very confused.
> +}
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