From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1221722B8DF; Mon, 7 Sep 2026 17:23:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788801790; cv=none; b=pNNb8Nqskv378poKizDO2IElxbYab+mkPPNRtoX9Tqg9bCAdfUtQB6IWvq1uEGG1ZkpBzl0R985Wgu96DPzCZyOazhP9Ut2hHUXoWmUdIl45NUyYhbjVnmL/2/VOvVCKrdrPduFHo8OFB/t9bkzkodY1goSJcHdEBNgLJJcwzN8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788801790; c=relaxed/simple; bh=IsgOz23jgtxh6t9JZSP6IEO1hhjpWphaC5Zz14LTxIA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F+kVfYm0r7WcSEZcidio1tr1aab1VL2+RQnXv5gqMLaJgJ8a2A4xOimGGoMp8pTac0MtQtn4YSNkCfPA8EDLNURNEyB8liqNuS3mY5J+J5jECog75uHcLg5v7R7j30zJqIexVYwnOLi7LymceBwKVBRs6rQXyLit+KPrxYQ+kas= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=is3AQ3HR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="is3AQ3HR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A85A81F00A3A; Mon, 7 Sep 2026 17:23:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788801788; bh=jG1ZK2ISJn6wMPTOrAsRj6Xemqw0VX1VQJjjXEJrdqI=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=is3AQ3HRDL8a5qjAFDPNCBSxvXnEkEAF6pensEMfbTchD579zlSjf9oOqFTPjeiAq 5Jpt9yv5e2caI5XsQlAqevq6KgyP6qnMe9W5VzUptoAePYvJ4G9mM/kp09TNKWtQna rMBEdnuwGeg1Vr++2Pgyf57XTYZcUoVW4hQPdktosMHfpiAqb8NXdrpC6kCZC8FmZr emVfrv8AZ/2gXivDasel+ImYMDm/Az7CIgzitPAq4P/wr3vgd9uR6+WjwXpJgYrcXv 8ihuis1zkLjK1GJ/Mfj8XbmrHh3Vc2l2UwU2TqL7qIDpnTVJhrq43sPNhi5lPVazus t6PJWoJgIElWA== Message-ID: <948c60be-5e45-45b1-823a-7599f7c7fd38@kernel.org> Date: Mon, 7 Sep 2026 19:23:00 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/5] mm: Make per-VMA locks available universally To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: dave.hansen@linux.intel.com, Liam.Howlett@oracle.com, ljs@kernel.org, willy@infradead.org, shakeel.butt@linux.dev, vbabka@kernel.org, jannh@google.com, aliceryhl@google.com, arve@android.com, cmllamas@google.com, christian@brauner.io, tkjos@android.com, dsahern@kernel.org, davem@davemloft.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org References: <20260813193433.3318288-1-surenb@google.com> <20260813193433.3318288-2-surenb@google.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 On 8/13/26 21:34, Suren Baghdasaryan wrote: > From: Dave Hansen > > The per-VMA locks have been around for several years. They've had some > bugs worked out of them and have seen quite wide use. However, they > are still only available when architectures explicitly enable them. > Remove the conditional compilation around the per-VMA locks, making > them available on all architectures and configs. > > The approach up to now seemed to be to add ARCH_SUPPORTS_PER_VMA_LOCK > when the architecture started using per-VMA locks in the fault > handler. But, contrary to the naming, the Kconfig option does not > really indicate whether the architecture supports per-VMA locks or > not. It is more of a marker for whether the architecture is likely to > benefit from per-VMA locks. > > To me, the most important thing side-effect of universal availability > is letting per-VMA locks be used in SMP=n configs. This lets us use > per-VMA locking in all x86 code without fallbacks. > > Overall, this just generally makes the kernel simpler. Just look at > the diffstat. It also opens the door to users that want to use the > per-VMA locks in common code. Doing *that* brings additional > simplifications. > > The downside of this is adding some fields to vm_area_struct and > mm_struct. There are likely ways to optimize this, especially for > things like SMP=n configs. For now, do the simplest thing: use the > same implementation everywhere. > > == Considerations for NOMMU config == Maybe the NOMMU "support" could have been had in a separate prep patch (where a lot of the description below could have been moved), making the patch itself just mostly a removal of code. Acked-by: David Hildenbrand (Arm) -- Cheers, David