From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932628AbaFINjO (ORCPT ); Mon, 9 Jun 2014 09:39:14 -0400 Received: from fw-tnat.austin.arm.com ([217.140.110.23]:12140 "EHLO collaborate-mta1.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750720AbaFINjM (ORCPT ); Mon, 9 Jun 2014 09:39:12 -0400 Date: Mon, 9 Jun 2014 14:38:59 +0100 From: Catalin Marinas To: Leif Lindholm Cc: "msalter@redhat.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Will Deacon , "steve.capper@linaro.org" Subject: Re: [PATCH] arm64: Add flush_cache_vmap call in __early_set_fixmap Message-ID: <20140609133859.GB18487@localhost> References: <1402050590-23877-1-git-send-email-leif.lindholm@linaro.org> <1402065449.15402.2.camel@deneb.redhat.com> <20140606145324.GE4179@bivouac.eciton.net> <1402067373.15402.9.camel@deneb.redhat.com> <20140609110356.GD25590@arm.com> <20140609132429.GF4179@bivouac.eciton.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140609132429.GF4179@bivouac.eciton.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 09, 2014 at 02:24:29PM +0100, Leif Lindholm wrote: > On Mon, Jun 09, 2014 at 12:03:56PM +0100, Catalin Marinas wrote: > > A quick grep through the kernel shows that we have other set_pte() calls > > without additional dsb() like create_mapping(), I think kvm_set_pte() as > > well. > > > > So I'm proposing an alternative patch (which needs some benchmarking as > > well to see if anything is affected, maybe application startup time). > > I'm happy for any fix which can be included in 3.16. Steve Capper made a point about performance. He'll follow up. > But is the dsb(ishst) sufficient? We need to also prevent reads from > overtaking the set_pte(). i.e.: > > ptr = early_ioremap(phys_addr, size); > if (ptr && strcmp(ptr, "magic") == 0) > ... > > Does it not require a dsb(ish)? So doesn't early_ioremap() now include a dsb() after set_pte() with my patch? BTW, according to the ARM ARM (and confirmed with architects), we needs DSB+ISB even if we have just a data access (rather than instruction fetch). We have to revisit both 32 and 64-bit code for this. -- Catalin