From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id A40BE6B026A for ; Tue, 17 Jul 2018 11:59:04 -0400 (EDT) Received: by mail-ed1-f72.google.com with SMTP id b12-v6so731285edi.12 for ; Tue, 17 Jul 2018 08:59:04 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com. [148.163.158.5]) by mx.google.com with ESMTPS id r17-v6si1196401edd.405.2018.07.17.08.59.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Jul 2018 08:59:03 -0700 (PDT) Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6HFsXBP105124 for ; Tue, 17 Jul 2018 11:59:01 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0b-001b2d01.pphosted.com with ESMTP id 2k9j7xkxsf-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 17 Jul 2018 11:59:01 -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 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 Content-Transfer-Encoding: 8bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: 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 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