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 X-Spam-Level: X-Spam-Status: No, score=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D89BC433E0 for ; Mon, 1 Feb 2021 17:24:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC9D364EA9 for ; Mon, 1 Feb 2021 17:24:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229646AbhBARYH (ORCPT ); Mon, 1 Feb 2021 12:24:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229645AbhBARYF (ORCPT ); Mon, 1 Feb 2021 12:24:05 -0500 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20215C061756 for ; Mon, 1 Feb 2021 09:23:26 -0800 (PST) Received: by mail-pl1-x62b.google.com with SMTP id e12so1177339pls.4 for ; Mon, 01 Feb 2021 09:23:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9E0GZTfD0OA02q73XXsHXPjWkg/VrnXV/UimqNs2u/E=; b=gD0R+WWEXz93nBxxqPBDVQT6VZbWF3Vv2AWFZvd6W9pd+B1ZaM4BGwle4Pk7bOF8+2 stK3J3hDPr6/aBUPPT4cl7IM0VwDMrX4upH4rVJHdGqoJC9Tm581hivIMePcLze2jGNM 6pmxfOCJI1jMM1aniPHomJd6y3IOULNVturxxiEoCE0K9y/iJjanCpS9mNNYi2YvEYuu R5b+YA21oFlyGwVmOB5qUN0Ph5WtluSj6+FRGl8ktvIMRv1XJjhtegwT4iTw1jnV/J+A QHXrBIjTVTRu5KYBBzK/ELZqLdW1PZRvcC08xOoURS41hoVl0WXAXcpZtB35xax/al2C eWXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9E0GZTfD0OA02q73XXsHXPjWkg/VrnXV/UimqNs2u/E=; b=I2I/qPlTKLLjSlsOh/1QavUSe2O8vGoTLazcHaF8EaseSRRiTFCUEeuITZI7FMJ0NE Qp93YcM3G3cLE3H8E4250ukr9T5u6qF9z83fjSLtu3q4PT0gO3pMJRGNNeud2d0aJm9I ZXgD9Ynm1jb7a9KYUZeNmRy2dPxu2nv7zvzhVXanmbsy620G2Kh4fTXtnhMkJeUnH6ly YB5S+JqZ9KD1kknfTErS4UONfif5utD/ejKyoVYMflUbaT/daL7q7/dXMQeyJA/JSeiv P1UJBnNf6g8xj5LZx1ijHLAPohnK2S712dvpBKCEvyPqrqm+euquoOUjHeh/UPNYjcAq 3HVQ== X-Gm-Message-State: AOAM533e1qrS/6BXg0JOlWPsMnNhqJ6uo6h5qxFsJoCTjS9dzKXlnOP/ doEDhhzL67SkUlOc8bjbjTPfeg== X-Google-Smtp-Source: ABdhPJyG6qMXCDzBhJ1M0vVcr+ePuvV5kkvchzwtbizMAl9r4GNA0R6P5SlGZ7XjJH/oeWz81Md4uA== X-Received: by 2002:a17:90b:1955:: with SMTP id nk21mr12832220pjb.206.1612200205533; Mon, 01 Feb 2021 09:23:25 -0800 (PST) Received: from google.com ([2620:15c:f:10:829:fccd:80d7:796f]) by smtp.gmail.com with ESMTPSA id m11sm16404799pjz.44.2021.02.01.09.23.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Feb 2021 09:23:24 -0800 (PST) Date: Mon, 1 Feb 2021 09:23:18 -0800 From: Sean Christopherson To: Dave Hansen Cc: Kai Huang , Jarkko Sakkinen , linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, luto@kernel.org, haitao.huang@intel.com, pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com Subject: Re: [RFC PATCH v3 08/27] x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled Message-ID: References: <5076ed2c486ac33bfd87dc0e17047a1673692b53.1611634586.git.kai.huang@intel.com> <20210201184040.646ea9923c2119c205b3378d@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Feb 01, 2021, Dave Hansen wrote: > On 1/31/21 9:40 PM, Kai Huang wrote: > >>> - ret = sgx_drv_init(); > >>> + /* Success if the native *or* virtual EPC driver initialized cleanly. */ > >>> + ret = !!sgx_drv_init() & !!sgx_vepc_init(); > >> If would create more dumb code and just add > >> > >> ret = sgx_vepc_init() > >> if (ret) > >> goto err_kthread; > > Jarkko, I'm not sure I understand this suggestion. > > > Do you mean you want below? > > > > ret = sgx_drv_init(); > > ret = sgx_vepc_init(); > > if (ret) > > goto err_kthread; > > > > This was Sean's original code, but Dave didn't like it. The problem is it's wrong. That snippet would incorrectly bail if drv_init() succeeds but vepc_init() fails. The alternative to the bitwise AND is to snapshot the result in two separate variables: ret = sgx_drv_init(); ret2 = sgx_vepc_init(); if (ret && ret2) goto err_kthread; or check the return from drv_init() _after_ vepc_init(): ret = sgx_drv_init(); if (sgx_vepc_init() && ret) goto err_kthread; As evidenced by this thread, the behavior is subtle and easy to get wrong. I deliberately chose the option that was the weirdest specifically to reduce the probability of someone incorrectly "cleaning up" the code. > Are you sure? I remember the !!&!! abomination being Sean's doing. :) Yep! That 100% functionally correct horror is my doing. > > Sean/Dave, > > > > Please let me know which way you prefer. > > Kai, I don't really know you are saying here. In the end, > sgx_vepc_init() has to run regardless of whether sgx_drv_init() is > successful or not. Also, we only want to 'goto err_kthraed' if *BOTH* > fail. The code you have above will, for instance, 'goto err_kthread' if > sgx_drv_init() succeeds but sgx_vepc_init() fails. It entirely > disregards the sgx_drv_init() error code.