Re: [patch V4 part 3 09/29] x86/entry/32: Provide macro to emit IDT entry stubs

Mathieu Desnoyers
2020-05-14T14:43:40Z

----- Thomas Gleixner <tglx@linutronix.de> wrote:
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
> > ----- On May 14, 2020, at 12:31 AM, Andy Lutomirski luto@kernel.org wrote:
> >> On Wed, May 13, 2020 at 6:44 PM Mathieu Desnoyers
> >> <mathieu.desnoyers@efficios.com> wrote:
> >> They're needed for all entries except SYSCALL, but they're hidden
> >> inside helpers in many cases.
> >
> > Indeed, on x86-32 the macro SAVE_ALL contains cld. That architecture
> > appears to be OK.
> >
> > What I am concerned about is the idtentry, idtentry_mce_db,
> > and idtentry_df macros introduced in entry_64.S by this series.
> > Those are supposed to be technically equivalent to the prior
> > code, which indeed has the ASM_CLAC but no "cld".
> >
> > So maybe the cld happens to be hidden elsewhere, but I'm clearly
> > missing it ? Or is it not needed for some reason ?
>
> It's needed and it is there where it was forever in error_entry and
> paranoid_entry.

Ok I simply missed it.

>
> It probably makes sense to stick it right after the CLAC.

Indeed.

Thanks!

Mathieu

>
> Thanks,
>
> tglx
>
>

--
Mathieu Desnoyers
EfficiOS Inc.