From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8DCCE226D01 for ; Mon, 10 Mar 2025 10:55:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741604124; cv=none; b=ma/VM81zK8ZkRo+N2zMb+TKjs0qPyVr+WxNayAvxvvM/J3PYsPd5ofFGKYWiccuqaofpsxje8UpHZTF9e3+XcSg5iwKkAGUqdZUKs9XSA+OoxytOetH7fbMqvOoLJYQCtMiYq/xCKuqX+grbf1HKbSgB8Oz5Ib+AkpQfT2qgTbY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741604124; c=relaxed/simple; bh=nVETkI4hsbHPO6L/vVLLdSvKCZk8H9YIi7LVwjeCefA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=W8PLeQLqSaWsr2om89/b5PrEz4b1aoW2SIvU/chSpJdIkzVGyvosJMgN+GYgh2RgckSQdvGL9aXWmJ0cGW5WUrADmuPkU4V9cdHLHQUUBQZo7fUvhoHIkW8WV4EkNQPrxV5ISJL0IUpfWu5vSD1u41O07jdKV/z7KH4QwqASEmw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 51490153B; Mon, 10 Mar 2025 03:55:33 -0700 (PDT) Received: from J2N7QTR9R3.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 930B93F5A1; Mon, 10 Mar 2025 03:55:20 -0700 (PDT) Date: Mon, 10 Mar 2025 10:55:18 +0000 From: Mark Rutland To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Ryan Roberts , Ard Biesheuvel , linux-kernel@vger.kernel.org Subject: Re: [PATCH V2] arm64/mm: Create level specific section mappings in map_range() Message-ID: References: <20250310062812.216031-1-anshuman.khandual@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250310062812.216031-1-anshuman.khandual@arm.com> On Mon, Mar 10, 2025 at 11:58:12AM +0530, Anshuman Khandual wrote: > Currently PMD section mapping mask i.e PMD_TYPE_SECT is used while creating > section mapping at all page table levels except the last level. This works > fine as the section mapping masks are exactly the same (0x1UL) for all page > table levels. > > This will change in the future with D128 page tables that have unique skip > level values (SKL) required for creating section mapping at different page > table levels. Hence use page table level specific section mapping macros > instead of the common PMD_TYPE_SECT. While here also ensure that a section > mapping is only created on page table levels which could support that on a > given page size configuration otherwise fall back to create table entries. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ryan Roberts > Cc: Ard Biesheuvel > Cc: linux-kernel@vger.kernel.org > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Anshuman Khandual > --- > This patch applies on v6.14-rc6 > > Changes in V2: > > - Dropped PGD_TYPE_SECT macro and its instance from map_range() > - Create table entries on levels where section mapping is not possible On the last version, there was talk of an extant bug: https://lore.kernel.org/all/5f1b36e2-6455-44d9-97b0-253aefd5024f@arm.com/ ... did that turn out to not be the case? > > Changes in V1: > > https://lore.kernel.org/all/20250303041834.2796751-1-anshuman.khandual@arm.com/ > > arch/arm64/kernel/pi/map_range.c | 38 +++++++++++++++++++++++++++++--- > 1 file changed, 35 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c > index 2b69e3beeef8..25a70c675c4d 100644 > --- a/arch/arm64/kernel/pi/map_range.c > +++ b/arch/arm64/kernel/pi/map_range.c > @@ -11,6 +11,22 @@ > > #include "pi.h" > > +static bool sect_supported(int level) What exactly is this function supposed to indicate? Due to the 'default' case, it'll return true for level-3 tables where sections/blocks aren't possible, but pages are. So maybe this is just misnamed, and wants to be something like "leaf_supported()" ? > +{ > + switch (level) { > + case -1: > + return false; > + case 0: > + if (IS_ENABLED(CONFIG_ARM64_16K_PAGES) || > + IS_ENABLED(CONFIG_ARM64_64K_PAGES)) > + return false; > + else > + return true; Surely: case 0: return IS_ENABLED(CONFIG_ARM64_4K_PAGES); ... though that's only the case when LPA2 is supported and TCR_ELx.DS is set. > + default: > + return true; As above, what is this supposed to return for level-3 tables where sections/blocks aren't possible? Can we BUILD_BUG() for bogus levels? > + } > +} > + > /** > * map_range - Map a contiguous range of physical pages into virtual memory > * > @@ -44,13 +60,29 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot, > * Set the right block/page bits for this level unless we are > * clearing the mapping > */ > - if (protval) > - protval |= (level < 3) ? PMD_TYPE_SECT : PTE_TYPE_PAGE; > + if (protval && sect_supported(level)) { The existing code is trying to find the leaf prot for a given level of table, so as-is checking sect_supported() is at best misleading. If we're going to do something different below based on sect_supported(), I reckon this should be moved into the path where sect_supported() returned true, maybe factored out into a helper for clarity. Mark. > + switch (level) { > + case 3: > + protval |= PTE_TYPE_PAGE; > + break; > + case 2: > + protval |= PMD_TYPE_SECT; > + break; > + case 1: > + protval |= PUD_TYPE_SECT; > + break; > + case 0: > + protval |= P4D_TYPE_SECT; > + break; > + default: > + break; > + } > + } > > while (start < end) { > u64 next = min((start | lmask) + 1, PAGE_ALIGN(end)); > > - if (level < 3 && (start | next | pa) & lmask) { > + if ((level < 3 && (start | next | pa) & lmask) || !sect_supported(level)) { > /* > * This chunk needs a finer grained mapping. Create a > * table mapping if necessary and recurse. > -- > 2.25.1 > >