From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 71399C6FA86 for ; Mon, 5 Sep 2022 07:22:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235459AbiIEHWK (ORCPT ); Mon, 5 Sep 2022 03:22:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236305AbiIEHVX (ORCPT ); Mon, 5 Sep 2022 03:21:23 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 442044361D for ; Mon, 5 Sep 2022 00:17:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=t2PBhD4tG/Sd24mg1y9JF8kau2tsDVuXNdrrbtxRewM=; b=IVfI9ofbUPorJudsRSnYUmlPQb +DRzmycivKykc+D3XRRW7S3HoB9XAEKk8HM0xkyWfW2YyrvPvnXqzC+43jA6rVL25ZXgALFdeLxX5 paqeqJrU0ORJBXh9l/OjrUrKTmaBqcnTbHJGSZz6lpC4QtvOayEktfHUGMDnrhmrSD4yQu+QcsxEX h/nvEwMXa3h8mDe8oOlhpRYqQkFr8iLtTGZ308//XRUm1q6L6ku7ABbga4kBYveJ8+zgSqsJwIg8O 3wYt84jFZ5S8kr7ujom/9JX6PDszuThwbpQ0c9Hg6NatiwcatjzgNjWC/hZzeR1lL0+BKLjqdcgX7 CHnqcm2A==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1oV6Le-009Sra-9A; Mon, 05 Sep 2022 07:16:47 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BCA203001FD; Mon, 5 Sep 2022 09:16:43 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 79AF42B63D24B; Mon, 5 Sep 2022 09:16:43 +0200 (CEST) Date: Mon, 5 Sep 2022 09:16:43 +0200 From: Peter Zijlstra To: Linus Torvalds Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org, Tim Chen , Josh Poimboeuf , Andrew Cooper , Pawan Gupta , Johannes Wikner , Alyssa Milburn , Jann Horn , "H.J. Lu" , Joao Moreira , Joseph Nuzman , Steven Rostedt , Juergen Gross , Masami Hiramatsu , Alexei Starovoitov , Daniel Borkmann , K Prateek Nayak , Eric Dumazet Subject: Re: [PATCH v2 37/59] x86/putuser: Provide room for padding Message-ID: References: <20220902130625.217071627@infradead.org> <20220902130950.205726504@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 03, 2022 at 10:26:45AM -0700, Linus Torvalds wrote: > On Fri, Sep 2, 2022 at 2:46 PM Linus Torvalds > wrote: > > > > Hmm. It doesn't look too horrible, but yeah, fi it still ends up > > getting the same padding overhead I'm not sure it ends up really > > mattering. > > Oh, and I think it's buggy anyway. > > If there are any tail-calls to a leaf function, the tracking now gets > out of whack. So it's no longer a "don't bother counting the last > level", now it ends up being a "count got off by one". See validate_sibling_call(), it too calls validate_call(). (Although prehaps I should go s/sibling/tail/ on all that for clarity)