From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACDE0C282EC for ; Fri, 14 Mar 2025 12:57:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D22B280002; Fri, 14 Mar 2025 08:57:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 97FB5280001; Fri, 14 Mar 2025 08:57:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 87237280002; Fri, 14 Mar 2025 08:57:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 6A058280001 for ; Fri, 14 Mar 2025 08:57:51 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 764A2B875C for ; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 8750720003 X-Stat-Signature: ju83t31kzr9dwgoz6u8foch4b977xfmx X-Rspamd-Server: rspam06 X-HE-Tag: 1741957070-303612 X-HE-Meta: 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 sy0h2eSq GjkSEkXtoNeDdKf3MLXK3FDUOfvBvk8Cla9CIUGWdAa0fWLkHMWVlwE3r0jPOjgRTGa8JLsNBrnIpMDTeznf4ZE4yGtNyf+qgoysxh+ISvNgNYyAEydn7vuMJhqi9CjMkItDMv/GS17V2Hwg32XNWQMA9eeBJj68qgj7+QBpn0yCtCAuWX7dJK6wW2eP2+SfZyi6x X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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 14/03/25 2:14 am, Matthew Wilcox wrote: > On Thu, Mar 13, 2025 at 11:44:14PM +0530, Dev Jain wrote: >> Since pxd_clear_bad() is an operation changing the state of the page tables, >> we should call arch_sync_kernel_mappings() post this. > > Could you explain why? What effect does not calling > arch_sync_kernel_mappings() have in this case? Apologies, I again forgot to explain the userspace effect. I just found this by code inspection, using the logic the fixes commit uses: we should sync when we change the pxd. The question I have been pondering on is, what is the use of the pxd_bad() macros, when do we actually hit a bad state, and why don't we just trigger a BUG when we hit pxd_bad()?