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Tue, 24 Jun 2025 12:00:04 +0000 (GMT) Date: Tue, 24 Jun 2025 14:00:02 +0200 From: Alexander Gordeev To: David Hildenbrand Cc: Dev Jain , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: move mask update out of the atomic context Message-ID: References: <20250623080440.3005693-1-agordeev@linux.ibm.com> <4214d6d6-f8d5-43b3-a413-f576fdaf215d@redhat.com> <75717e4e-51d0-41a2-8463-45097fc3875b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <75717e4e-51d0-41a2-8463-45097fc3875b@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: fazFq2rDNT2-PW9A3uQh3Z2JthCXtzj0 X-Proofpoint-GUID: fazFq2rDNT2-PW9A3uQh3Z2JthCXtzj0 X-Authority-Analysis: v=2.4 cv=BpqdwZX5 c=1 sm=1 tr=0 ts=685a9346 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=6IFa9wvqVegA:10 a=nENOSrSBMpMrXF5MCvkA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjI0MDA5OSBTYWx0ZWRfX4glAbsng8hlX eVa8iwvTyWlWgTV7SdMAOK5zofZZQ+x7Px7ly2qJprQQBL8+IQEQKOmPIyyiDnLrKLL5WjsImvX rGYyVrz0kpzlONRJscUOmR2TlW3+CyVNSKkKnn9iKSoah6Wc/fDxl8ukidaN3pULmR67/k4IsWO R3vdGZZETXvoV4njFxtmB02DppTJLUKfq3Yh2hCktazFSZbbcdu+tCp1wudbZKlGRrfgaZifedR zxP8IedlotmWNjHWqj6nVOJBdmeH8KNxSKJ5shUdgSPlXc+hR1GrzsFGfB38p1uDw5xfNi5esWe r2Xg10seD+i/aAjx1oVwryCKf1HX3pymYA8CAI5jTl8o9mx/FCj+aHgE27Oj6Fq2QvuxLoY/ZLW 7LYkyan5uVbloe8w2EryraeRLnS9L6bl6klF0Beu4AP3KJRr7aQFkyX5vOGwcDgwKBW1YCJs X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.7,FMLib:17.12.80.40 definitions=2025-06-24_04,2025-06-23_07,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 lowpriorityscore=0 impostorscore=0 clxscore=1015 spamscore=0 mlxlogscore=383 priorityscore=1501 phishscore=0 malwarescore=0 adultscore=0 bulkscore=0 suspectscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506240099 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DED4F100008 X-Stat-Signature: cmgfo6gwiujsk87g5a8g45c4zpfgu6wy X-Rspam-User: X-HE-Tag: 1750766410-705453 X-HE-Meta: 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 92wxnAEB c1+RmzG18h4ZFEgg7nj0BpW03khZ6qC7tvOKwJDH/GdnzIL1ZOQ0aUnnAUmz//JRJk7HcznPy2R8MjFhFrfDTpSTGLdCeSLC/8NCVMYfUKa6X+o7/29d0m4QrrS0DGH7pSMOrmbKBRLj9gM8B33G7N+ntj6Y2HjO98jEW/IZ0kBzNGngb8KRlM3BA7w9mheh3acUl8NQXOsp+BCfSS3qL4Ph5hwuG2/97S/zMCH7TTBagiIHtQzXhulAnO1+dP1C9swF4bCj5H+RDehCBG6bxccoQMvr/vU2MghrkGJ5zYvnKCvmKcslUJ1bTLUQewmDVLg9E X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 24, 2025 at 11:40:05AM +0200, David Hildenbrand wrote: > On 24.06.25 11:37, Alexander Gordeev wrote: > > On Mon, Jun 23, 2025 at 09:45:34PM +0200, David Hildenbrand wrote: > > ... > > > Let's ask the real questions: who checks PGTBL_PTE_MODIFIED? > > > > > > I see > > > > > > if (mask & ARCH_PAGE_TABLE_SYNC_MASK) > > > arch_sync_kernel_mappings(start, start + size); > > > > > > And then > > > > > > arch/arm/include/asm/page.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED > > > arch/x86/include/asm/pgtable-2level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED > > > arch/x86/include/asm/pgtable-3level_types.h:#define ARCH_PAGE_TABLE_SYNC_MASK PGTBL_PMD_MODIFIED > > > > > > > > > Which makes me wonder why we need PGTBL_PTE_MODIFIED at all? Is there some other check I am missing? > > > > > > (same question regarding everything excepy PGTBL_PMD_MODIFIED, because that actually seems to be used) > > > > AFAICT it was thought as architecture-specific: > > > > /* > > * Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values > > * and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings() > > * needs to be called. > > */ > > #ifndef ARCH_PAGE_TABLE_SYNC_MASK > > #define ARCH_PAGE_TABLE_SYNC_MASK 0 > > #endif > > > > Not sure if that needs to be addressed at all. > > Okay, if there are no users of PGTBL_PTE_MODIFIED we could just ... remove > it. Dead code. As you noticed, PGTBL_PMD_MODIFIED bit is used only. Thus, all other bits would have to be removed as well, not just PGTBL_PTE_MODIFIED? That is more or less revert of at least the below commits and rewriting it in a PMD-focused manner: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified") d8626138009b ("mm: add functions to track page directory modifications") That would be a completely different effort, which I am not aming at ;) > -- > Cheers, > > David / dhildenb Thanks!