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 X-Spam-Level: X-Spam-Status: No, score=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 077ACC4320A for ; Thu, 12 Aug 2021 23:39:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D686A6109F for ; Thu, 12 Aug 2021 23:39:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238715AbhHLXjU (ORCPT ); Thu, 12 Aug 2021 19:39:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:49056 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238492AbhHLXib (ORCPT ); Thu, 12 Aug 2021 19:38:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4087A61131; Thu, 12 Aug 2021 23:38:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628811485; bh=7WJKlO9bHU1KTACHVSZNKYdiOMEX5YhZuZxQV/SdLuA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Dt1uufFxiBpM64WdTSAuTk8+1zrKO6HU17TYlEUlNN2kujLxQYptBPWGS+0DQsO8c qLICm2qZyETLEzLvScOtCQYp5JedDoefi3B5ziqpYXQusDyQeCNzXRPINiFGzyB0ik AIsE96Dk0G2t12AyO1Ka1LfR5NFh9OOSpW0+yL/l0+qDRko4spy5cH0V3OuvtRJ3Fg nIKGR1NJko/owd0DL01zdM6HsvN6k862UPaFztDZw0p5ZGHiObtNREUaZCUqexrveP m580WAdbM/F0mF37GPiVk2k5f33D1sPQrkwPSbiJSQCipodfYOi5O5jCZ9SrkyCP0n GSOvLOSh6E24w== From: Vineet Gupta To: linux-snps-arc@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Anshuman Khandual , Mike Rapoport , Vineet Gupta Subject: [PATCH v2 18/19] ARC: mm: vmalloc sync from kernel to user table to update PMD ... Date: Thu, 12 Aug 2021 16:37:52 -0700 Message-Id: <20210812233753.104217-19-vgupta@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210812233753.104217-1-vgupta@kernel.org> References: <20210812233753.104217-1-vgupta@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ... not PGD vmalloc() sets up the kernel page table (starting from @swapper_pg_dir). But when vmalloc area is accessed in context of a user task, say opening terminal in n_tty_open(), the user page tables need to be synced from kernel page tables so that TLB entry is created in "user context". The old code was doing this incorrectly, as it was updating the user pgd entry (first level itself) to point to kernel pud table (2nd level), effectively yanking away the entire user space translation with kernel one. The correct way to do this is to ONLY update a user space pgd/pud/pmd entry if it is not popluated already. This ensures that only the missing leaf pmd entry gets updated to point to relevant kernel pte table. >From code change pov, we are chaging the pattern: p4d = p4d_offset(pgd, address); p4d_k = p4d_offset(pgd_k, address); if (!p4d_present(*p4d_k)) goto bad_area; set_p4d(p4d, *p4d_k); with p4d = p4d_offset(pgd, address); p4d_k = p4d_offset(pgd_k, address); if (p4d_none(*p4d_k)) goto bad_area; if (!p4d_present(*p4d)) set_p4d(p4d, *p4d_k); Signed-off-by: Vineet Gupta --- arch/arc/mm/fault.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index f8994164fa36..5787c261c9a4 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -36,31 +36,31 @@ noinline static int handle_kernel_vaddr_fault(unsigned long address) pgd = pgd_offset(current->active_mm, address); pgd_k = pgd_offset_k(address); - if (!pgd_present(*pgd_k)) + if (pgd_none (*pgd_k)) goto bad_area; - - set_pgd(pgd, *pgd_k); + if (!pgd_present(*pgd)) + set_pgd(pgd, *pgd_k); p4d = p4d_offset(pgd, address); p4d_k = p4d_offset(pgd_k, address); - if (!p4d_present(*p4d_k)) + if (p4d_none(*p4d_k)) goto bad_area; - - set_p4d(p4d, *p4d_k); + if (!p4d_present(*p4d)) + set_p4d(p4d, *p4d_k); pud = pud_offset(p4d, address); pud_k = pud_offset(p4d_k, address); - if (!pud_present(*pud_k)) + if (pud_none(*pud_k)) goto bad_area; - - set_pud(pud, *pud_k); + if (!pud_present(*pud)) + set_pud(pud, *pud_k); pmd = pmd_offset(pud, address); pmd_k = pmd_offset(pud_k, address); - if (!pmd_present(*pmd_k)) + if (pmd_none(*pmd_k)) goto bad_area; - - set_pmd(pmd, *pmd_k); + if (!pmd_present(*pmd)) + set_pmd(pmd, *pmd_k); /* XXX: create the TLB entry here */ return 0; -- 2.25.1