From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41VQ221KtCzF3Hb for ; Wed, 18 Jul 2018 01:59:04 +1000 (AEST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6HFsld9016045 for ; Tue, 17 Jul 2018 11:59:02 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2k9ggqgv2x-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 17 Jul 2018 11:59:02 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 17 Jul 2018 16:59:00 +0100 Date: Tue, 17 Jul 2018 08:58:48 -0700 From: Ram Pai To: Dave Hansen Cc: shuahkh@osg.samsung.com, linux-kselftest@vger.kernel.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, mingo@redhat.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, fweimer@redhat.com, msuchanek@suse.de, aneesh.kumar@linux.vnet.ibm.com Subject: Re: [PATCH v13 08/24] selftests/vm: fix the wrong assert in pkey_disable_set() Reply-To: Ram Pai References: <1528937115-10132-1-git-send-email-linuxram@us.ibm.com> <1528937115-10132-9-git-send-email-linuxram@us.ibm.com> <3c441309-1d35-eead-0c5d-1d7d20018219@intel.com> MIME-Version: 1.0 In-Reply-To: <3c441309-1d35-eead-0c5d-1d7d20018219@intel.com> Message-Id: <20180717155848.GA5790@ram.oc3035372033.ibm.com> Content-Type: text/plain; charset=us-ascii List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Jun 20, 2018 at 07:47:02AM -0700, Dave Hansen wrote: > On 06/13/2018 05:44 PM, Ram Pai wrote: > > If the flag is 0, no bits will be set. Hence we cant expect > > the resulting bitmap to have a higher value than what it > > was earlier > ... > > if (flags) > > - pkey_assert(read_pkey_reg() > orig_pkey_reg); > > + pkey_assert(read_pkey_reg() >= orig_pkey_reg); > > dprintf1("END<---%s(%d, 0x%x)\n", __func__, > > pkey, flags); > > } > > This is the kind of thing where I'd love to hear the motivation and > background. This "disable a key that was already disabled" operation > obviously doesn't happen today. What motivated you to change it now? On powerpc, hardware supports READ_DISABLE and WRITE_DISABLE. ACCESS_DISABLE is basically READ_DISABLE|WRITE_DISABLE on powerpc. If access disable is called on a key followed by a write disable, the second operation becomes a nop. In such cases, read_pkey_reg() == orig_pkey_reg Hence the code above is modified to pkey_assert(read_pkey_reg() >= orig_pkey_reg); -- Ram Pai