From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=eZ3S=UF=vger.kernel.org=linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT
	autolearn=ham autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 6A541C04AB5
	for <linux-kernel@archiver.kernel.org>; Thu,  6 Jun 2019 09:38:36 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 46064208E3
	for <linux-kernel@archiver.kernel.org>; Thu,  6 Jun 2019 09:38:36 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1727882AbfFFJif (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 6 Jun 2019 05:38:35 -0400
Received: from foss.arm.com ([217.140.101.70]:43918 "EHLO foss.arm.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727359AbfFFJif (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 6 Jun 2019 05:38:35 -0400
Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249])
        by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BCFA4341;
        Thu,  6 Jun 2019 02:38:34 -0700 (PDT)
Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249])
        by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 659FD3F690;
        Thu,  6 Jun 2019 02:38:33 -0700 (PDT)
Date:   Thu, 6 Jun 2019 10:38:11 +0100
From:   Mark Rutland <mark.rutland@arm.com>
To:     Catalin Marinas <catalin.marinas@arm.com>
Cc:     Anshuman Khandual <anshuman.khandual@arm.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Will Deacon <will.deacon@arm.com>,
        James Morse <james.morse@arm.com>,
        Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH V2 3/4] arm64/mm: Consolidate page fault information
 capture
Message-ID: <20190606093811.GA37430@lakrids.cambridge.arm.com>
References: <1559544085-7502-1-git-send-email-anshuman.khandual@arm.com>
 <1559544085-7502-4-git-send-email-anshuman.khandual@arm.com>
 <20190604144209.GJ6610@arrakis.emea.arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190604144209.GJ6610@arrakis.emea.arm.com>
User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jun 04, 2019 at 03:42:09PM +0100, Catalin Marinas wrote:
> On Mon, Jun 03, 2019 at 12:11:24PM +0530, Anshuman Khandual wrote:
> > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > index da02678..4bb65f3 100644
> > --- a/arch/arm64/mm/fault.c
> > +++ b/arch/arm64/mm/fault.c
> > @@ -435,6 +435,14 @@ static bool is_el0_instruction_abort(unsigned int esr)
> >  	return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW;
> >  }
> >  
> > +/*
> > + * This is applicable only for EL0 write aborts.
> > + */
> > +static bool is_el0_write_abort(unsigned int esr)
> > +{
> > +	return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM);
> > +}
> 
> What makes this EL0 only?

It returns false for EL1 faults caused by DC IVAC, where write
permission is required. EL0 can only issue maintenance that requires
read permission.

For whatever reason, the architecture says that WnR is always 1b1, even
if read permission was sufficient.

How about:

/*
 * Note: not valid for EL1 DC IVAC, but we never use that such that it
 * should fault.
 */
static bool is_write_abort(unsigned int esr)
{
	return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM);
}

... which would also address your concern about EL1 writes to a user
mapping.

Thanks,
Mark.