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Wed, 17 May 2023 07:58:27 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BEA6420040; Wed, 17 May 2023 07:58:27 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B3F8E2004B; Wed, 17 May 2023 07:58:26 +0000 (GMT) Received: from [9.179.22.107] (unknown [9.179.22.107]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 17 May 2023 07:58:26 +0000 (GMT) Message-ID: <6a6f5552fac1427eafbca1288fe5d5cb0cb6a333.camel@linux.ibm.com> Subject: Re: [PATCH v5 RESEND 10/17] s390: mm: Convert to GENERIC_IOREMAP From: Niklas Schnelle To: Christoph Hellwig , Baoquan He Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, arnd@arndb.de, christophe.leroy@csgroup.eu, agordeev@linux.ibm.com, wangkefeng.wang@huawei.com, David.Laight@aculab.com, shorne@gmail.com, willy@infradead.org, deller@gmx.de, Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org Date: Wed, 17 May 2023 09:58:26 +0200 In-Reply-To: References: <20230515090848.833045-1-bhe@redhat.com> <20230515090848.833045-11-bhe@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.48.1 (3.48.1-1.fc38) MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: yHkOOiLn5K_XXg82H6WtpYBwMUNzSS4k X-Proofpoint-GUID: zbqUKTFztHSElm1UI7AZo0AwloZJ5dPG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-16_14,2023-05-16_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 bulkscore=0 clxscore=1011 malwarescore=0 suspectscore=0 lowpriorityscore=0 spamscore=0 phishscore=0 mlxscore=0 impostorscore=0 mlxlogscore=729 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2304280000 definitions=main-2305170061 X-Stat-Signature: 8osnx3chrihapocey8txptzibdcwng7e X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2FFAD100008 X-Rspam-User: X-HE-Tag: 1684310342-253878 X-HE-Meta: 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 8WpKwpjt x8XAnS2EuUxJRixq9YfAb0qS/z0iOsdInGgQXwoWh1jlZicj0p8D3+JdlcXAnGFukyqzY1BGa9G4WCcfszZ/PCQUczzcdn4GVpcea54//mCoUCNA6UxUoam38unwp1J+mgMcP8kuB80Y+DmGAS+xoklVtnCLLGWWNtaGI5NdNzfHRPcFjZm7okK5rrw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000017, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 2023-05-16 at 23:36 -0700, Christoph Hellwig wrote: > On Mon, May 15, 2023 at 05:08:41PM +0800, Baoquan He wrote: > > +#define ioremap_wc(addr, size) \ > > + ioremap_prot((addr), (size), pgprot_val(pgprot_writecombine(PAGE_KERN= EL))) >=20 > I'd move this out of line and just apply mio_wb_bit_mask directly > instead of the unbox/box/unbox/box dance. >=20 > > +#define ioremap_wt(addr, size) \ > > + ioremap_prot((addr), (size), pgprot_val(pgprot_writethrough(PAGE_KERN= EL))) >=20 > and just define this to ioremap_wc. Note that defining _wt to _wc is > very odd and seems wrong, but comes from the existing code. Maybe the > s390 maintainers can chime on on the background and we can add a comment > while we're at it. I'm a bit confused where you see ioremap_wt() defined to ioremap_wc() in the existing code? Our current definitions are: void __iomem *ioremap_wc(phys_addr_t addr, size_t size) { return __ioremap(addr, size, pgprot_writecombine(PAGE_KERNEL)); } void __iomem *ioremap_wt(phys_addr_t addr, size_t size) { return __ioremap(addr, size, pgprot_writethrough(PAGE_KERNEL)); } Now if we don't have support for the enhanced PCI load/store instructions (memory I/O aka MIO) then yes this gets ignored and both .._wc() and .._wt() act the same but if we do have them pgprot_writecombine() / pgprot_writethrough() set respectively clear=20 the mio_wb bit in the PTE. It's a bit odd here because the exact position of the bit is read from a firmware interface and could in theory change but other than that it looks fine to me and yes I agree that it would be odd and broken to define _wt to _wc. Thanks, Niklas