From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 3A05E29A1 for ; Thu, 18 Apr 2024 06:50:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713423058; cv=none; b=R5ex1+HnnG1rkR+OgHtI0PZ1u+rDsYGkiLGMkf5K/NVwDgvGKHpfG2U+0cN/AR7P9ttxdvvX+qDN+NtG8t167mO7C9hYK38CYQRYYTfcR4vd4x+tZR/J/2RjjfItlQWc8CO0YWrgZ+cPLVECYtONHNdlJyu8mTyM+uPr9Tv4VFw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713423058; c=relaxed/simple; bh=WaYWNrxAeIq3qm2grzE5tnanXShMVTdyKXEkKKhPw10=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bes5iMpv/8eGKSRNqL+OrVU+LwUgzExUYXerVw8294CCCXB/8yfLruWGFzsdaZgav3CP/CiEcJYE/xMcVH+tJxAHT6YsaJd2I3lssrB2q2GXirqHz32ubAs+J/UHmVngaqrPEjl9B3u63cb18TbJFmz2vSryu/a4yao8Pujzb3I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Q/WYvIij; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Q/WYvIij" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=WaYWNrxAeIq3qm2grzE5tnanXShMVTdyKXEkKKhPw10=; b=Q/WYvIij6klQ9NVt6qf8y9T6r9 EJlUweKDuguJCdtSmulpV6aybwqEQvG/RCNNr0mluynz8arRxX3LOEZaAjHnyALc1mTkWUxeVEZxS 0kRTuCGmOPlOUFrIU1D+lP6WElaukeqYmxMjF9DpAmJCskXZhbdK9uA+dhqWy0hKP3Bx4v/QB7s9b fxThAlYH8/Oa0tRPtdyYE91fDnRbkPPWSvOyQ43+QlrC0lfvLGelfdNoZFMElo42sPcUFdExcfIUZ 70BlBvqG5z+5SMcTXmFG4vCGuA+9x17LGlzln7371TDbSn7X1hwMk3odyZE9DUjvf3G8Ub/C9Ifth Squll11w==; Received: from hch by bombadil.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rxLbj-00000001BIg-0Wsv; Thu, 18 Apr 2024 06:50:55 +0000 Date: Wed, 17 Apr 2024 23:50:55 -0700 From: Christoph Hellwig To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , Daniel Sneddon , Pawan Gupta , Thomas Gleixner , Alexandre Chartre , Konrad Rzeszutek Wilk , Peter Zijlstra , Greg Kroah-Hartman , Sean Christopherson , Andrew Cooper , Dave Hansen , Nikolay Borisov , KP Singh , Waiman Long , Borislav Petkov , Ingo Molnar Subject: Re: [PATCH v3] x86/bugs: Only harden syscalls when needed Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Apr 16, 2024 at 04:02:21PM -0700, Josh Poimboeuf wrote: > Syscall hardening (i.e., converting the syscall indirect branch to a > series of direct branches) may cause performance regressions in certain > scenarios. Maybe spell out the scenarios, as this just sounds like hand waiving right now..