From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 415013A1BA; Tue, 20 Aug 2024 01:46:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724118411; cv=none; b=GcVRFakRT9dkOA2MYsoLX6TMGEKUfXXHZUzF/XbOw2ISHE69GOTJM65wmkjTXkN3WKWtYrtM7q1gM4efNtIPb66Q/uDzzY/VBEsISkxgNWbpuOWIqoZAEn++Y544sbL3UUW1entapshDCKdRYudgl9RwGLiKzvrFYCtY7j30uNM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724118411; c=relaxed/simple; bh=rA2KKwezxMOw6UPaznb0hf7DP0Mow7wiG3m7yVXGBTk=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=tOECHzSKw4qVcL9HQMeWEWpHNGceouxNb2krax47WLRnfVXwqbokouX8pHOaPQxSXpj/nGoX/EVcStA0w29/QGTCmVOiEC3IDwboSdXVq3y3P8hVGzujnwfHr9wHUaskLE/0JY5CRU0ke/X/LmKtVz7Le3VXQ4UznQfHW8ktV+I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=jix3qp/N; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="jix3qp/N" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C77A6C32782; Tue, 20 Aug 2024 01:46:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1724118410; bh=rA2KKwezxMOw6UPaznb0hf7DP0Mow7wiG3m7yVXGBTk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=jix3qp/NdvOwD3MXE1iLaiyPurkDmKXMgyvVN5f6craLLKdZ4RrJQ9PJhZcGbVwjj S71p0O32+TVGOhmo1o2Wh2YKmM1YEvC7gHbpUlnNNC+Xont7T1qFz9csoVPDFZhkv6 C5TYeg7PHhn+Ys+rvHXw6L0TOosywYTW7NVJQ1Vk= Date: Mon, 19 Aug 2024 18:46:49 -0700 From: Andrew Morton To: Matthew Wilcox Cc: Suren Baghdasaryan , kent.overstreet@linux.dev, corbet@lwn.net, arnd@arndb.de, mcgrof@kernel.org, rppt@kernel.org, paulmck@kernel.org, thuth@redhat.com, tglx@linutronix.de, bp@alien8.de, xiongwei.song@windriver.com, ardb@kernel.org, david@redhat.com, vbabka@suse.cz, mhocko@suse.com, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, liam.howlett@oracle.com, pasha.tatashin@soleen.com, souravpanda@google.com, keescook@chromium.org, dennis@kernel.org, jhubbard@nvidia.com, yuzhao@google.com, vvvvvv@google.com, rostedt@goodmis.org, iamjoonsoo.kim@lge.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 5/5] alloc_tag: config to store page allocation tag refs in page flags Message-Id: <20240819184649.8fc7da59f89290f716ae0553@linux-foundation.org> In-Reply-To: References: <20240819151512.2363698-1-surenb@google.com> <20240819151512.2363698-6-surenb@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Mon, 19 Aug 2024 21:40:34 +0100 Matthew Wilcox wrote: > On Mon, Aug 19, 2024 at 01:39:16PM -0700, Suren Baghdasaryan wrote: > > On Mon, Aug 19, 2024 at 12:34 PM Matthew Wilcox wrote: > > > So if ALLOC_TAG_REF_WIDTH is big enough, it's going to force last_cpupid > > > into struct page. > > > > Thanks for taking a look! > > Yes, but how is this field different from say KASAN_TAG_WIDTH which > > can also force last_cpupid out of page flags? > > Because KASAN isn't for production use? > > > > That will misalign struct page and disable HVO -- with no warning! > > > > mminit_verify_pageflags_layout already has a mminit_dprintk() to > > indicate this condition. Is that not enough? > > Fair. Is a BUILD_BUG_ON() feasible here?