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 4C575C43458 for ; Fri, 26 Jun 2026 16:09:40 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=d2RpaOt1UY9w7z3P6fskDSOG9pDQRRmB1BEeBNxqJr4=; b=wqws+FFnEwk3NpadA/tbIzRTfm wbJ7Kx9+gZhB0/oNlizHekafnC3qTK8HLHLVYlF8hj9KahYipErdAqORM9Fi7JHpVzndLt97qJt4q BgoLwOYEwY1yvFV25ITDAdnK2X2GfEc5vwV0uTWf41tbVfLTVUOzmmPdevo8g7dPt90y9vhaMr3eH aguANUtjuiPHEDB+ZFfHpGwXsGGpaMJhXU/cVmpMXA/7DTiJaOjx/ZOMhQt7TnmKIyqAaw6YPQVuO 8ob247Aq2nQxP9ftrpQIV9NIYQY3/eBtmXdFoCZYFlvvojRGGgEsHP68GdnCDZW4mlR8ARwCjORNK bdQldyzQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wd97V-0000000Bb8U-257h; Fri, 26 Jun 2026 16:09:33 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wd97U-0000000Bb8O-1QCn for linux-arm-kernel@lists.infradead.org; Fri, 26 Jun 2026 16:09:32 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id E20D14358D; Fri, 26 Jun 2026 16:09:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8A7A1F000E9; Fri, 26 Jun 2026 16:09:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782490171; bh=d2RpaOt1UY9w7z3P6fskDSOG9pDQRRmB1BEeBNxqJr4=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=oZ4B++o/Kmjf4mUIAYR5+eeWqagv/Mf5xBAQhfNkRTB5OSZtAiNHppeTvnGpD6nVT eKHuClfS9exgUr7g18L8xjPcrTm0MWPChQNVvTURWTPWwZlE3UWx/DgyOzJ6vuDQux rjI+54clt8ILLbFApZu9/sMPQiaXSabVHsChhTMnSpPmlkzgRXZbqjQZDtxwk11Vli h5MOvr0rroF+HrZ1rEAF34RgdZFbJLoDOpCks+Jf51RpilDiRE0QeJz2PBz7Bku2tw pxDCbuPC9ToShir5k+Vybct8QvRoX1SaSa1V+QDbS6QXLl5j/YMFKXQO4+Wnpmn5S6 BSNDSKHuLnVxw== Message-ID: Date: Fri, 26 Jun 2026 18:09:27 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/mm: Optimize TLB flush in unmap_hotplug_[pmd|pud]_range() To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Ryan Roberts , linux-kernel@vger.kernel.org, Ben Hutchings References: <20260626012845.475959-1-anshuman.khandual@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit 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 6/26/26 03:28, Anshuman Khandual wrote: > flush_tlb_kernel_range() could flush down an entire block mapping just with > a single PAGE_SIZE stride. This capability was being used umapping PMD and > PUD based block mappings in unmap_hotplug_[pmd|pud]_range(). > > But later on the commit 48478b9f7913 > ("arm64/mm: Enable batched TLB flush in unmap_hotplug_range()") replaced > this PAGE_SIZE stride with [PMD|PUD]_SIZE strides, hence forcing multiple > PAGE_SIZE stride based TLB flushes on platforms where TLB range operation > is not supported. Revert back to the earlier TLB behaviour along with the > required comments that were dropped earlier. > Right, it looked like the right thing to do in that commit. I wonder if we can make the comments even clearer to prevent his happening another time, incorporating the HW consideration. In any case Reviewed-by: David Hildenbrand (Arm) > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: David Hildenbrand > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Reported-by: Ben Hutchings > Closes: https://lore.kernel.org/all/b0d5836032ce3135bfc473f6bff791306d086925.camel@decadent.org.uk/ > Fixes: 48478b9f7913 ("arm64/mm: Enable batched TLB flush in unmap_hotplug_range()") > Signed-off-by: Anshuman Khandual > --- > arch/arm64/mm/mmu.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 8242f93f05e4..5ff0041f4a5f 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1509,7 +1509,11 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr, > if (free_mapped) { > /* CONT blocks are not supported in the vmemmap */ > WARN_ON(pmd_cont(pmd)); > - flush_tlb_kernel_range(addr, addr + PMD_SIZE); > + /* > + * One TLBI should be sufficient here as the PMD_SIZE > + * range is mapped with a single block entry. > + */ "Flush only a single page, resulting in a single TLBi for this large block mapping, avoiding multiple TLBIs on HW without TLB range flushes." -- Cheers, David