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x-vs=clean score=-100 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfMNJYPSIsh0fUGSe3P13PkXXuTJ/9nigJXbJ48lgGA43n+TdiJJUvAk1R+CUrXvrYWoaeJGhpZ719yeNJivUzyieQR+buKKmuKIbgd2ou0mMsS3kJ9rH GxCgRwQO8ls8H3+ymrTgragB5uwYmK7rur7eSvG5JOQhj4BO7rjeJgidwie26vFjfEYj+EN03EI24S8iXEclRmzk4XfsZUS2CmYA6UUFGOnHkDf9XoXJXLpN X-CM-Analysis: v=2.3 cv=FKU1Odgs c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=kj9zAlcOel0A:10 a=Kd1tUaAdevIA:10 a=ErGtf2ZWZXZoqN4hRzUA:9 a=CjuIK1q_8ugA:10 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756535AbeDZOTc (ORCPT ); Thu, 26 Apr 2018 10:19:32 -0400 Received: from 8bytes.org ([81.169.241.247]:51914 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756431AbeDZOT2 (ORCPT ); Thu, 26 Apr 2018 10:19:28 -0400 Date: Thu, 26 Apr 2018 16:19:26 +0200 From: Joerg Roedel To: Toshi Kani Cc: mhocko@suse.com, akpm@linux-foundation.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, bp@suse.de, catalin.marinas@arm.com, guohanjun@huawei.com, will.deacon@arm.com, wxf.wang@hisilicon.com, willy@infradead.org, cpandya@codeaurora.org, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces Message-ID: <20180426141926.GN15462@8bytes.org> References: <20180314180155.19492-1-toshi.kani@hpe.com> <20180314180155.19492-3-toshi.kani@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180314180155.19492-3-toshi.kani@hpe.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi Toshi, Andrew, this patch(-set) is broken in several ways, please see below. On Wed, Mar 14, 2018 at 12:01:55PM -0600, Toshi Kani wrote: > Implement pud_free_pmd_page() and pmd_free_pte_page() on x86, which > clear a given pud/pmd entry and free up lower level page table(s). > Address range associated with the pud/pmd entry must have been purged > by INVLPG. An INVLPG before actually unmapping the page is useless, as other cores or even speculative instruction execution can bring the TLB entry back before the code actually unmaps the page. > int pud_free_pmd_page(pud_t *pud) > { > - return pud_none(*pud); > + pmd_t *pmd; > + int i; > + > + if (pud_none(*pud)) > + return 1; > + > + pmd = (pmd_t *)pud_page_vaddr(*pud); > + > + for (i = 0; i < PTRS_PER_PMD; i++) > + if (!pmd_free_pte_page(&pmd[i])) > + return 0; > + > + pud_clear(pud); TLB flush needed here, before the page is freed. > + free_page((unsigned long)pmd); > + > + return 1; > } > > /** > @@ -724,6 +739,15 @@ int pud_free_pmd_page(pud_t *pud) > */ > int pmd_free_pte_page(pmd_t *pmd) > { > - return pmd_none(*pmd); > + pte_t *pte; > + > + if (pmd_none(*pmd)) > + return 1; > + > + pte = (pte_t *)pmd_page_vaddr(*pmd); > + pmd_clear(pmd); Same here, TLB flush needed. Further this needs synchronization with other page-tables in the system when the kernel PMDs are not shared between processes. In x86-32 with PAE this causes a BUG_ON() being triggered at arch/x86/mm/fault.c:268 because the page-tables are not correctly synchronized. > + free_page((unsigned long)pte); > + > + return 1; > } > #endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */