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 078E12F8BF0 for ; Wed, 7 Jan 2026 09:13:57 +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=1767777240; cv=none; b=krIMcf1+jWk+d0hBdh5u0HCeodC+UKil8xz9OIQpMgmGsuM5BU9M+b2FeqhuCBYsAPxYR7KN2bOi7CmpAkwoXhlmSLvNH0wLWjqSdyHExefI5Z2DazLF5DNVM/gWG21M1WVwjR1C9tYc14y89Cee4sl94Va1kp2P0Z3UvwrwVSs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767777240; c=relaxed/simple; bh=ZF2J3kKvedFfRLHA7CJWZOLGPL7wErk5fVnaBzzYV2s=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=i+fD7e+dtq1Nm/SUaV4FyekxL3CYmpS4f9AbC+HAcog6SYAuCuMmVkss7KgJvLqSDpbV/yaJEc7vPQIre6xaEQcFa/aHTgfuWRjm1jXnVa92mefIviL6dN7P+JTK236cSfv0ewgvXwTAUUlgJ2rgysb8SX9f8fbeeehz9aX9NZs= 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 7053F497; Wed, 7 Jan 2026 01:13:50 -0800 (PST) Received: from [10.57.95.107] (unknown [10.57.95.107]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 23F533F5A1; Wed, 7 Jan 2026 01:13:55 -0800 (PST) Message-ID: <791773e4-9590-4093-a916-a02981633d16@arm.com> Date: Wed, 7 Jan 2026 09:13:54 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64/mm: Assert NR_BM_PUD_TABLES for bm_pud[] Content-Language: en-GB To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: mark.rutland@arm.com, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org References: <20260107061606.3160088-1-anshuman.khandual@arm.com> <32030401-06d3-40ad-a0b6-fbd366092f2b@arm.com> From: Ryan Roberts In-Reply-To: <32030401-06d3-40ad-a0b6-fbd366092f2b@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 07/01/2026 09:07, Anshuman Khandual wrote: > > > On 07/01/26 2:03 PM, Ryan Roberts wrote: >> On 07/01/2026 06:16, Anshuman Khandual wrote: >>> There is an implicit assumption about bm_pud[] being single entry PUD table >>> just like bp_pmd[] which is a single entry PMD table. Though only the later >>> gets asserted via NR_BM_PMD_TABLES. Hence let's add a similar check for PUD >>> table as well. >>> >>> Cc: Catalin Marinas >>> Cc: Will Deacon >>> Cc: linux-arm-kernel@lists.infradead.org >>> Cc: linux-kernel@vger.kernel.org >>> Signed-off-by: Anshuman Khandual >>> --- >>> arch/arm64/mm/fixmap.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c >>> index c5c5425791da..e02594be8b8e 100644 >>> --- a/arch/arm64/mm/fixmap.c >>> +++ b/arch/arm64/mm/fixmap.c >>> @@ -23,8 +23,11 @@ static_assert(FIXADDR_TOT_START > PCI_IO_END); >>> SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PMD_SHIFT) >>> #define NR_BM_PMD_TABLES \ >>> SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PUD_SHIFT) >>> +#define NR_BM_PUD_TABLES \ >>> + SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, P4D_SHIFT) >>> >>> static_assert(NR_BM_PMD_TABLES == 1); >>> +static_assert(NR_BM_PUD_TABLES == 1); >> >> But if there is only one PMD table, there must only be one PUD table (and one >> P4D table, and one PGD table) by definition. So I don't think this is checking >> anything that the existing PMD table check is not. > > Agreed but should not this check help tighten this code up given that bm_pud[] > array gets used for possible PUD entries ? I don't see the value of it myself, given the PMD assert is already doing the required check. > >> >> Thanks, >> Ryan >> >>> >>> #define __BM_TABLE_IDX(addr, shift) \ >>> (((addr) >> (shift)) - (FIXADDR_TOT_START >> (shift))) >> >