From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1163557AbdKRKqE convert rfc822-to-8bit (ORCPT ); Sat, 18 Nov 2017 05:46:04 -0500 Received: from szxga03-in.huawei.com ([45.249.212.189]:13360 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764675AbdKRKpw (ORCPT ); Sat, 18 Nov 2017 05:45:52 -0500 From: "Liuwenliang (Abbott Liu)" To: Christoffer Dall CC: Marc Zyngier , "linux@armlinux.org.uk" , "aryabinin@virtuozzo.com" , "afzal.mohd.ma@gmail.com" , "f.fainelli@gmail.com" , "labbott@redhat.com" , "kirill.shutemov@linux.intel.com" , "mhocko@suse.com" , "catalin.marinas@arm.com" , "akpm@linux-foundation.org" , "mawilcox@microsoft.com" , "tglx@linutronix.de" , "thgarnie@google.com" , "keescook@chromium.org" , "arnd@arndb.de" , "vladimir.murzin@arm.com" , "tixy@linaro.org" , "ard.biesheuvel@linaro.org" , "robin.murphy@arm.com" , "mingo@kernel.org" , "grygorii.strashko@linaro.org" , "glider@google.com" , "dvyukov@google.com" , "opendmb@gmail.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "kasan-dev@googlegroups.com" , "linux-mm@kvack.org" , Jiazhenghua , Dailei , Zengweilin , Heshaoliang Subject: Re: [PATCH 01/11] Initialize the mapping of KASan shadow memory Thread-Topic: [PATCH 01/11] Initialize the mapping of KASan shadow memory Thread-Index: AQHTXujfZ5ece1W6v0+GfMCIss4ZwaMXzeBA///bmgCAAkGXsA== Date: Sat, 18 Nov 2017 10:40:08 +0000 Message-ID: References: <8e959f69-a578-793b-6c32-18b5b0cd08c2@arm.com> <87a7znsubp.fsf@on-the-bus.cambridge.arm.com> <87po8ir1kg.fsf@on-the-bus.cambridge.arm.com> <87375eqobb.fsf@on-the-bus.cambridge.arm.com> <20171117073556.GB28855@cbox> In-Reply-To: <20171117073556.GB28855@cbox> Accept-Language: en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.57.90.243] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020204.5A100E1B.00BD,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=169.254.11.85, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 656b33ec11cc64de7e525d8b592277a7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Nov 17, 2017 15:36 Christoffer Dall [mailto:cdall@linaro.org] wrote: >If your processor does support LPAE (like a Cortex-A15 for example), >then you have both the 32-bit accessors (MRC and MCR) and the 64-bit >accessors (MRRC, MCRR), and using the 32-bit accessor will simply access >the lower 32-bits of the 64-bit register. > >Hope this helps, >-Christoffer If you know the higher 32-bits of the 64-bits cp15's register is not useful for your system, then you can use the 32-bit accessor to get or set the 64-bit cp15's register. But if the higher 32-bits of the 64-bits cp15's register is useful for your system, then you can't use the 32-bit accessor to get or set the 64-bit cp15's register. TTBR0/TTBR1/PAR's higher 32-bits is useful for CPU supporting LPAE. The following description which comes from ARM(r) Architecture Reference Manual ARMv7-A and ARMv7-R edition tell us the reason: 64-bit TTBR0 and TTBR1 format: ... BADDR, bits[39:x] : Translation table base address, bits[39:x]. Defining the translation table base address width on page B4-1698 describes how x is defined. The value of x determines the required alignment of the translation table, which must be aligned to 2x bytes. Abbott Liu: Because BADDR on CPU supporting LPAE may be bigger than max value of 32-bit, so bits[39:32] may be valid value which is useful for the system. 64-bit PAR format ... PA[39:12] Physical Address. The physical address corresponding to the supplied virtual address. This field returns address bits[39:12]. Abbott Liu: Because Physical Address on CPU supporting LPAE may be bigger than max value of 32-bit, so bits[39:32] may be valid value which is useful for the system. Conclusion: Don't use 32-bit accessor to get or set TTBR0/TTBR1/PAR on CPU supporting LPAE, if you do that, your system may run error.