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Fri, 17 Jul 2020 09:42:43 -0400 (EDT) Received: from mail03.efficios.com (mail03.efficios.com [167.114.26.124]) by mail.efficios.com (Postfix) with ESMTP id 13F0629F31E; Fri, 17 Jul 2020 09:42:43 -0400 (EDT) Date: Fri, 17 Jul 2020 09:42:43 -0400 (EDT) From: Mathieu Desnoyers To: Nicholas Piggin Cc: Peter Zijlstra , Anton Blanchard , Arnd Bergmann , linux-arch , linux-kernel , linux-mm , linuxppc-dev , Andy Lutomirski , Andy Lutomirski , x86 Message-ID: <1314561373.18530.1594993363050.JavaMail.zimbra@efficios.com> In-Reply-To: <1594906688.ikv6r4gznx.astroid@bobo.none> 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> Subject: Re: [RFC PATCH 4/7] x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_3955 (ZimbraWebClient - FF78 (Linux)/8.8.15_GA_3953) Thread-Topic: x86: use exit_lazy_tlb rather than membarrier_mm_sync_core_before_usermode Thread-Index: tih2wG5S7/k8ds/ZwlGdEfhVUfBRJg== X-Rspamd-Queue-Id: 69547180F8BAB X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: ----- 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