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 822E23B83E1; Thu, 10 Sep 2026 10:09:12 +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=1789034956; cv=none; b=QTE3j7GQDyPWGTdzKiZh+Z0EZ8sdF+zm3CReLTRV7OqeU0eYbUiJriBQZQf/Dabf4tCFk3N9fin1W67tPg7XVr3adRZOGq/59MiwgFRBijNSWJdzxHXNhDK1gNfw7Zd0C9IM2L6mBmGrLLhKgiuNUFDpZSubN0er1c0jbRpeaGs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789034956; c=relaxed/simple; bh=SanV6Fhu23pLSQRWIhb8Asmcvxgi/KUzHqg8LOqvZk8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OxAzAIcwj2F/v2BkQE/Ax7Ee9+WNJBoxn6SJRhKkEqjukYmt7sRt5jZ+4dBMi13naO8drv/JmRTkBG3nx9MW5ISWjwHpLXqcxYwepzR0CpKsR6EAog1NkqW+cdSTZAE+4CJdPXEkKSqlGAfMZi0SHEJajvipRgaa904AJNhyZzk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BAOxyzNV; 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="BAOxyzNV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1D8C31F000FF; Thu, 10 Sep 2026 10:09:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789034950; bh=b9PGX3cvQTKEp1StomMC/PUuNY3LIk1gdRQb5hd00+M=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BAOxyzNVBmdk0w4Ok8N6GqK+3kwon4WEcnxstz+r/TqzWTPlAHxm+HOGFc01l/A77 RQTg3M3ldGn4sB9a9QHOqudnvyDNwWz4Qvp+9FfBqU5zxaRIQTIQ48juQh+1laj8sL w/5VaC34duOFKT4kTvGC9QsZO1IwYZsuFzjo7XJTUUkViDCw4cZgBrjT+HU2g3+oOI IuwbNPTaPc87hlZ24/4dYFFFL+bl+5rg79QkXtq56ZKwhU4YPOIcGG8SLKPpEi5csw HU6JWoPT4olrK0Xm5qRwntLlk5vV6MU9bPsYT5MHC/mlTY9BxWf53tdHfC41G9ngs8 xEfpJ+9TdcOhQ== Message-ID: Date: Thu, 10 Sep 2026 12:09:03 +0200 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 v7 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: <20260831203056.838265-1-surenb@google.com> <20260831203056.838265-2-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 8/31/26 22:30, 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 == Echoing what I commented on v6 after v7 was already sent (not realizing there was a v7 after my inbox got flooded) 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