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 50577171099 for ; Tue, 30 Apr 2024 12:53:35 +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=1714481617; cv=none; b=WeDewyNNArdLyrW6DgJxpypmpF0g2htxHOIs2dAKNaYqk+292zuNSEtXcMfbSVxYWUu/SJGpyEv6tR/FQMTEM6lVLghKUoe1MNYnw3WYhE5ssuQGeSZSvlJJxBFf+m4dVU6h/RGEZ7nFSVlmkF4qSmNH1Z9ILFyqhzt0WZMCfdY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714481617; c=relaxed/simple; bh=KUAYMhvovsY69EuC837OWjSCKrwjtcfZZJDSNCJrkjs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sQasvdUxjd5m0KBgmDq6aD/2AZFtCLvTmN/1Ib4Kus9UjNYhkhaXwUFIj2oQjpj7rb/uc9tp/1pIvhFcDa3uBlNRjR/KfYf+CsVaTiZy2hzB08YNA2lXuTX3VAtQVT7kbvgkwj8NM5PMomuNMEZJQGDDQhJKaK0San2NZ+0lm2o= 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 DD7CF2F4; Tue, 30 Apr 2024 05:54:01 -0700 (PDT) Received: from [10.1.38.140] (XHFQ2J9959.cambridge.arm.com [10.1.38.140]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E44CF3F793; Tue, 30 Apr 2024 05:53:33 -0700 (PDT) Message-ID: Date: Tue, 30 Apr 2024 13:53:32 +0100 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 v2 1/3] arm64/mm: Refactor PMD_PRESENT_INVALID and PTE_PROT_NONE bits Content-Language: en-GB To: David Hildenbrand , Catalin Marinas Cc: Will Deacon , Joey Gouly , Ard Biesheuvel , Mark Rutland , Anshuman Khandual , Peter Xu , Mike Rapoport , Shivansh Vij , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20240429140208.238056-1-ryan.roberts@arm.com> <20240429140208.238056-2-ryan.roberts@arm.com> <839d6975-ce12-4fc9-aa3b-8ec5787bf577@arm.com> <29fd6909-73d2-4b7e-99ef-0101cde1ba8a@redhat.com> From: Ryan Roberts In-Reply-To: <29fd6909-73d2-4b7e-99ef-0101cde1ba8a@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 30/04/2024 12:37, David Hildenbrand wrote: > On 30.04.24 13:11, Catalin Marinas wrote: >> On Mon, Apr 29, 2024 at 06:15:45PM +0100, Ryan Roberts wrote: >>> On 29/04/2024 17:20, Catalin Marinas wrote: >>>> On Mon, Apr 29, 2024 at 03:02:05PM +0100, Ryan Roberts wrote: >>>>> diff --git a/arch/arm64/include/asm/pgtable-prot.h >>>>> b/arch/arm64/include/asm/pgtable-prot.h >>>>> index dd9ee67d1d87..de62e6881154 100644 >>>>> --- a/arch/arm64/include/asm/pgtable-prot.h >>>>> +++ b/arch/arm64/include/asm/pgtable-prot.h >>>>> @@ -18,14 +18,7 @@ >>>>>   #define PTE_DIRTY        (_AT(pteval_t, 1) << 55) >>>>>   #define PTE_SPECIAL        (_AT(pteval_t, 1) << 56) >>>>>   #define PTE_DEVMAP        (_AT(pteval_t, 1) << 57) >>>>> -#define PTE_PROT_NONE        (_AT(pteval_t, 1) << 58) /* only when >>>>> !PTE_VALID */ >>>>> - >>>>> -/* >>>>> - * This bit indicates that the entry is present i.e. pmd_page() >>>>> - * still points to a valid huge page in memory even if the pmd >>>>> - * has been invalidated. >>>>> - */ >>>>> -#define PMD_PRESENT_INVALID    (_AT(pteval_t, 1) << 59) /* only when >>>>> !PMD_SECT_VALID */ >>>>> +#define PTE_INVALID        (_AT(pteval_t, 1) << 59) /* only when >>>>> !PTE_VALID */ >>>> >>>> Nitpick - I prefer the PTE_PRESENT_INVALID name as it makes it clearer >>>> it's a present pte. We already have PTE_VALID, calling it PTE_INVALID >>>> looks like a negation only. >>> >>> Meh, for me the pte can only be valid or invalid if it is present. So it's >>> implicit. And if you have PTE_PRESENT_INVALID you should also have >>> PTE_PRESENT_VALID. >>> >>> We also have pte_mkinvalid(), which is core-mm-defined. In your scheme, surely >>> it should be pte_mkpresent_invalid()? >>> >>> But you're the boss, I'll change this to PTE_PRESENT_INVALID. :-( >> >> TBH, I don't have a strong opinion but best to avoid the bikeshedding. >> I'll leave the decision to you ;). It would match the pmd_mkinvalid() >> core code. But if you drop 'present' make sure you add a comment above >> that it's meant for present ptes. > > FWIW, I was confused by > > present = valid | invalid OK fair enough. > > Something like > > present = present_valid | present_invalid I don't want to change pte_valid() to pte_present_valid(); that would also be a fair bit of churn. I'll take Catalin's suggestion and make this PTE_PRESENT_INVALID and pte_present_invalid(). And obviously leave pmd_mkinvalid() as it is. (Conversation in the other thread has concluded that it's ok to invalidate a non-present pmd afterall). > > would be more obvious at least to me ;) >