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 E4D97CDB47F for ; Wed, 24 Jun 2026 16:30:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mbyuAlSoRh47aaPkX7JF2oGMTEIdF1Zcr15uiIt8usA=; b=GJdIzqPSh9tUk5L/eztG49mmze PS6nQG8hQh7JIZeVFXljHSIs1UEvO+RuljROg/sbou4kznsA3dSGAnwPc8oZ+ChBuoNEmzUAIIuz9 0054XKtvg6/9/LzpzdWUG4hWZUcDwWHYsDUvQVRCg1tUpvAqUte6yI088Unm460J38OCuelkHhhmO xKufhbhXhoaRsnGreJWJ9LCTDDyCZ6Bnds9rP2O/CptizGAbciawJMzVzy0NOiADSnBv+29oSoyb1 LmW8x2KLgcEnxIAup/FeewbNO7cLuI6YZwIRpMrg7CeuwsHKT1Ma8TlcFbHOMb868g5fDrRfRoq6x lYPHVf9g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wcQUR-000000086Kb-0hg7; Wed, 24 Jun 2026 16:30:15 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wcQUP-000000086KC-0pIF for linux-arm-kernel@lists.infradead.org; Wed, 24 Jun 2026 16:30:13 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 7CB3260123; Wed, 24 Jun 2026 16:30:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 939161F00AC4; Wed, 24 Jun 2026 16:30:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1782318612; bh=mbyuAlSoRh47aaPkX7JF2oGMTEIdF1Zcr15uiIt8usA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=od2yYyf/sl8pz4IJPQDnQOrhYkXrpXNEKFtjPgBBO8QmuXmuUJUW1LX14FDxlYUHS Kw2kXlsRYdoRkjieZwt375+G5/EYfc5MLvG0MXBfetqiJGWAU7reZ5yiJUSXhZyrRO V9QwT7TTke2/Ucc705VGL2T6GpiWzVWpsj62SWyo= Date: Wed, 24 Jun 2026 17:29:00 +0100 From: Greg Kroah-Hartman To: Ryan Roberts Cc: Will Deacon , Ben Hutchings , Anshuman Khandual , Catalin Marinas , "David Hildenbrand (Arm)" , patches@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Sasha Levin , stable , mark.rutland@arm.com Subject: Re: [PATCH 6.1 337/522] arm64/mm: Enable batched TLB flush in unmap_hotplug_range() Message-ID: <2026062451-bluff-coherent-672d@gregkh> References: <20260616145125.307082728@linuxfoundation.org> <20260616145141.584613180@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 24, 2026 at 04:05:01PM +0100, Ryan Roberts wrote: > On 23/06/2026 15:25, Will Deacon wrote: > > On Sun, Jun 21, 2026 at 05:02:27PM +0200, Ben Hutchings wrote: > >> On Tue, 2026-06-16 at 20:28 +0530, Greg Kroah-Hartman wrote: > >>> 6.1-stable review patch. If anyone has any objections, please let me know. > >>> > >>> ------------------ > >>> > >>> From: Anshuman Khandual > >>> > >>> [ Upstream commit 48478b9f791376b4b89018d7afdfd06865498f65 ] > >> [...] > >>> @@ -949,15 +953,14 @@ static void unmap_hotplug_pmd_range(pud_ > >>> WARN_ON(!pmd_present(pmd)); > >>> if (pmd_sect(pmd)) { > >>> pmd_clear(pmdp); > >>> - > >>> - /* > >>> - * One TLBI should be sufficient here as the PMD_SIZE > >>> - * range is mapped with a single block entry. > >>> - */ > >>> - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > >>> - if (free_mapped) > >>> + if (free_mapped) { > >>> + /* CONT blocks are not supported in the vmemmap */ > >>> + WARN_ON(pmd_cont(pmd)); > >>> + flush_tlb_kernel_range(addr, addr + PMD_SIZE); > >> > >> It wasn't clear to me from the commit message why this now adds PMD_SIZE > >> rather than PAGE_SIZE. It seems like this change is fine for Linux > >> 6.13+ with a CPU that supports TLB range flushing, but otherwise results > >> in unnecessarily executing multiple TLB invalidations at intervals of > >> the base page size. > > > > Hmm, the commit message also makes very little sense to me and so I don't > > understand why this patch has us doing multiple TLB invalidations when > > we run into a !cont, block mapping at the PMD level. The old comment > > (which this patch removes) should still apply afaict. > > > > Anshuman, Ryan, any ideas what's going on here? > > I think this change was probably my fault; Given the API is called > flush_tlb_kernel_range() it seemed like an abuse/hack to pretend we are only > flushing the first PAGE_SIZE of the range. But as I understand it, even if the > HW shatters a block mapping into multiple TLB entries, all of the entries > relating to the block mapping will be invalidated if just one of them intersects > the TLBI range/address. So it should be safe to reapply this hack. > > Although ideally I think it would be better if this API took a stride argument; > then intent is clear. > > What's the best way to handle this? Submit a patch for mainline that reverts > this part, then get it backported to stable (implying this current patch will > have been applied to stable)? yes, that's probably the best way. thanks, greg k-h