From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [RFC PATCH 4/7] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode Date: Fri, 17 Jul 2020 09:42:43 -0400 (EDT) Message-ID: <1314561373.18530.1594993363050.JavaMail.zimbra@efficios.com> References: <1594868476.6k5kvx8684.astroid@bobo.none> <20200716085032.GO10769@hirez.programming.kicks-ass.net> <1594892300.mxnq3b9a77.astroid@bobo.none> <20200716110038.GA119549@hirez.programming.kicks-ass.net> <1594906688.ikv6r4gznx.astroid@bobo.none> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail.efficios.com ([167.114.26.124]:50558 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726079AbgGQNmo (ORCPT ); Fri, 17 Jul 2020 09:42:44 -0400 In-Reply-To: <1594906688.ikv6r4gznx.astroid@bobo.none> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Nicholas Piggin Cc: Peter Zijlstra , Anton Blanchard , Arnd Bergmann , linux-arch , linux-kernel , linux-mm , linuxppc-dev , Andy Lutomirski , Andy Lutomirski , x86 ----- On Jul 16, 2020, at 7:26 PM, Nicholas Piggin npiggin@gmail.com wrote: [...] > > membarrier does replace barrier instructions on remote CPUs, which do > order accesses performed by the kernel on the user address space. So > membarrier should too I guess. > > Normal process context accesses like read(2) will do so because they > don't get filtered out from IPIs, but kernel threads using the mm may > not. But it should not be an issue, because membarrier's ordering is only with respect to submit and completion of io_uring requests, which are performed through system calls from the context of user-space threads, which are called from the right mm. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com