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 1D166C05027 for ; Wed, 8 Feb 2023 21:08:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230393AbjBHVId (ORCPT ); Wed, 8 Feb 2023 16:08:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42142 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229617AbjBHVIc (ORCPT ); Wed, 8 Feb 2023 16:08:32 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D41014204 for ; Wed, 8 Feb 2023 13:08:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; 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=TZfyKMUGiouu3tkOyOCg+/xt7EfY48mH/8KV82A43Ak=; b=mhZ2VqtLu2DMBZTOVbgsfZVUYF 78WBqXmxkKz13X+r+xqqs9cAdxGO/nicfY57D47z10mno0Kgnijvpx/IJd1e3mRX2bqEcAG0zt2jo NlhYH5ZaVtz12ABGyOao8GqcQLBK46uWwbiz1b4urWC4KYuVRwULA8BLulRk7ZMml3sWt1ldFi+/x dNnEPKkrXaIc/KXfN8l5sqjPH3QXDB3ZoqdYlKWXRkkcdEADEqs3uFO5u5bDbL1tBtmf4P8Byp884 oi9nqYdlAstAjrhm2DuOcjHYk5GEuUD6aqjMGU9Q/LmB2KTZNh9XR7iiMDyAoM9wOeT3b+Ip7Yhdo zRBcoCcw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1pPrfp-001Y4A-F9; Wed, 08 Feb 2023 21:08:14 +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)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 9CA563001CB; Wed, 8 Feb 2023 22:08:12 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 803F6209BAB68; Wed, 8 Feb 2023 22:08:12 +0100 (CET) Date: Wed, 8 Feb 2023 22:08:12 +0100 From: Peter Zijlstra To: Andrew.Cooper3@citrix.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, mhiramat@kernel.org, kirill.shutemov@linux.intel.com, jpoimboe@redhat.com Subject: Re: [PATCH v3 3/4] x86/alternative: Rewrite optimize_nops() some Message-ID: References: <20230208171050.490809180@infradead.org> <20230208171431.373412974@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 Wed, Feb 08, 2023 at 09:44:04PM +0100, Peter Zijlstra wrote: > [ 11.584069] SMP alternatives: ffffffff82000095: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.590068] SMP alternatives: ffffffff820001f3: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.720069] SMP alternatives: ffffffff8200189f: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.731069] SMP alternatives: ffffffff820019ae: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.738069] SMP alternatives: ffffffff82001a4a: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.746069] SMP alternatives: ffffffff82001b2d: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.766069] SMP alternatives: ffffffff82001d14: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.770069] SMP alternatives: ffffffff82001dd5: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc > [ 11.779069] SMP alternatives: ffffffff82001f35: [0:20) optimized NOPs: eb 12 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc UNTRAIN_RET -- specifically RESET_CALL_DEPTH > [ 11.588621] SMP alternatives: ffffffff810026dc: [0:44) optimized NOPs: eb 2a cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cccc cc cc cc cc cc cc cc cc FILL_RETURN_BUFFER, and I'm thinking a 44 byte nop we ought to just jmp.