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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 093C0C3DA6E for ; Wed, 3 Jan 2024 21:55:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=lpfGLqnJDVQ4agiuXWQuj1pbc7FwQP//AOTttMMorpY=; b=FFTy/HjIeXHpBy 1tnsl/yEUib2y/7Pd2lrnSP+hEbx1K6olQBk32xeOd6v7EClLl7+RPzdyZEnSWtvhvc1TPqVsq0j6 Ovu7nbjp8Tpd10ZWuazhnS3RKXuG3Y4lfWwdQj3c2NurEWPvVolMW+Th8enlO8Fyt290gNb465Wxm 02r2pc1hV+2ekoRg2Xn2IvWitWN36JJC8u+kaqwZqZNeUBJ3P+3QVIPwPb93HkUquLdowyXKrjy9H usJTT5jBL4gjsnKEvHCTWtpoukpalHoDyCmvx2njmw8fK8Wf4XXlkXjO/dT+YYmqlOtMg5IIsNn8U 4OHb2eqmTKBZEi7UQiAA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rL9CG-00CCUT-05; Wed, 03 Jan 2024 21:54:44 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rL9CD-00CCT4-0S; Wed, 03 Jan 2024 21:54:42 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by ams.source.kernel.org (Postfix) with ESMTP id 83382B8161D; Wed, 3 Jan 2024 21:54:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCD1BC433C8; Wed, 3 Jan 2024 21:54:34 +0000 (UTC) Date: Wed, 3 Jan 2024 21:54:32 +0000 From: Catalin Marinas To: Dave Hansen Cc: Jisheng Zhang , Will Deacon , "Aneesh Kumar K . V" , Andrew Morton , Nick Piggin , Peter Zijlstra , Paul Walmsley , Palmer Dabbelt , Albert Ou , Arnd Bergmann , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Nadav Amit , Andrea Arcangeli , Andy Lutomirski , Dave Hansen , Thomas Gleixner , Yu Zhao , x86@kernel.org Subject: Re: [PATCH 1/2] mm/tlb: fix fullmm semantics Message-ID: References: <20231228084642.1765-1-jszhang@kernel.org> <20231228084642.1765-2-jszhang@kernel.org> <6ee6340a-ffe2-4106-b845-47cf443558c3@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <6ee6340a-ffe2-4106-b845-47cf443558c3@intel.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240103_135441_335691_9F8EECE2 X-CRM114-Status: GOOD ( 15.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jan 03, 2024 at 12:26:29PM -0800, Dave Hansen wrote: > On 1/3/24 10:05, Catalin Marinas wrote: > >> --- a/mm/mmu_gather.c > >> +++ b/mm/mmu_gather.c > >> @@ -384,7 +384,7 @@ void tlb_finish_mmu(struct mmu_gather *tlb) > >> * On x86 non-fullmm doesn't yield significant difference > >> * against fullmm. > >> */ > >> - tlb->fullmm = 1; > >> + tlb->need_flush_all = 1; > >> __tlb_reset_range(tlb); > >> tlb->freed_tables = 1; > >> } > > The optimisation here was added about a year later in commit > > 7a30df49f63a ("mm: mmu_gather: remove __tlb_reset_range() for force > > flush"). Do we still need to keep freed_tables = 1 here? I'd say only > > __tlb_reset_range(). > > I think the __tlb_reset_range() can be dangerous if it clears > ->freed_tables. On x86 at least, it might lead to skipping the TLB IPI > for CPUs that are in lazy TLB mode. When those wake back up they might > start using the freed page tables. You are right, I did not realise freed_tables is reset in __tlb_reset_range(). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel