linux-kernel - Re: Review of KPTI patchset

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Message-ID: <alpine.DEB.2.20.1712311513230.1899@nanos>
Date:   Sun, 31 Dec 2017 15:14:12 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Hugh Dickins <hughd@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Review of KPTI patchset

On Sun, 31 Dec 2017, Mathieu Desnoyers wrote:
> > Granted, it's not obvious and ideally we convert those this_cpu_read/writes
> > to __this_cpu_read/writes() to get the immediate fail reported on the first
> > access.
> 
> Indeed, if this function is expected to be called from non-preempt context,
> the __this_cpu_*() would be appropriate.
> 
> Moreover, clear_asid_other() could use a "static" definition, given that it's only ever
> used from arch/x86/mm/tlb.c:choose_new_asid(). Otherwise nothing prevents other users
> from unrelated areas of the kernel from calling it, and then we should document that
> preemption needs to be disabled around its invocation.
> 
> While we are there (discussing preemption and migration), I'm puzzled about the
> preempt_disable/enable in __native_flush_tlb(). First, it should cover the
> invalidate_user_asid() call too. Also, if the __ prefixed functions in this header

You're late to that discussion. That has been fixed already....

Thanks,

	tglx