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 00A56ECAAA1 for ; Mon, 31 Oct 2022 16:42:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231661AbiJaQmV (ORCPT ); Mon, 31 Oct 2022 12:42:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230440AbiJaQmS (ORCPT ); Mon, 31 Oct 2022 12:42:18 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 986692AC2 for ; Mon, 31 Oct 2022 09:42:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1667234537; x=1698770537; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=4Bordm8n7C3xVeQBvOSrA59fGvKoYiwKyVINkpri/O0=; b=VZIdpQkZxS2b3gM5m5ijvAsBfn4X9j3pShvxgUmJEnXOzxWqsdIwVgGd YytZXDzD8jh3kDAa6gm25vGAvjwY1q5Zfzp2dIRsp3CRj9AHRum6XDKGg vliTfP31ArQ2u3R5AJr7hWGUsHmpsB+b8eQkLs9v6c3r5oNNKRu1AU8/6 IZvGLTxABWgHlj7x+PxlTlij0Wqc3+2Gq2aNHeYBjKYyKTr49mFiqMCxI 2sXifC2Nn2aIwd9j5ueLKj69wgIgUaddUYMcKfIdoQ5bBfSP7UiPoqY4q 3ioOh95X56Q7Pk/i+StYf/E4bIkBvikTZu16MbLhSTh0iNbs3rsjXu5Uh A==; X-IronPort-AV: E=McAfee;i="6500,9779,10517"; a="310033805" X-IronPort-AV: E=Sophos;i="5.95,228,1661842800"; d="scan'208";a="310033805" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2022 09:42:17 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10517"; a="808611623" X-IronPort-AV: E=Sophos;i="5.95,228,1661842800"; d="scan'208";a="808611623" Received: from jfbondi-mobl1.amr.corp.intel.com (HELO [10.212.163.129]) ([10.212.163.129]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2022 09:42:16 -0700 Message-ID: <812cb868-1729-8d78-cf91-1e63c7933fae@intel.com> Date: Mon, 31 Oct 2022 09:42:15 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH 1/2] x86/tdx: Extract GET_INFO call from get_cc_mask() Content-Language: en-US To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, luto@kernel.org, peterz@infradead.org, sathyanarayanan.kuppuswamy@linux.intel.com, ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com, hpa@zytor.com, seanjc@google.com, thomas.lendacky@amd.com, elena.reshetova@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org References: <20221028141220.29217-1-kirill.shutemov@linux.intel.com> <20221028141220.29217-2-kirill.shutemov@linux.intel.com> <20221028235951.p2vdu7drbbf3ccg7@box.shutemov.name> <20221031041252.mdcjocqn6k4k4gvy@box.shutemov.name> From: Dave Hansen In-Reply-To: <20221031041252.mdcjocqn6k4k4gvy@box.shutemov.name> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/30/22 21:12, Kirill A. Shutemov wrote: > On Sat, Oct 29, 2022 at 02:59:51AM +0300, Kirill A. Shutemov wrote: >>> Can you please take a look through this and make sure I didn't botch >>> anything: >>> >>>> https://git.kernel.org/pub/scm/linux/kernel/git/daveh/devel.git/log/?h=tdxbadve >>> >>> The end result is about 50 lines less than what was there before. Most >>> of it is comment removal but the code is simpler too. >>> >>> Acks and Tested-by's would be appreciated. > > One thing that I must bring up is that it seems that there's no way to get > the panic message to user. I tried to convinced myself that it is qemu > misconfiguration on my part or some race, but no: it is just too early for > earlyprintk. > > We only get earlyprintk working after parse_early_options() which happens > well after tdx_early_init(). > > Moving panic() after earlyprintk working is not good idea as it exposes > kernel more: by the time we already have full #VE handler. How about we soften the panic() to a pr_err() if it's a debug guest? The first thing a user is going to do if they get an early boot failure is flip the debug switch and try it again. That gets us safe, well-defined behavior when we need security and also lets us figure out what went wrong. Also, did anyone ever actually implement that TDX earlyprintk simple console thing? A TDCALL up to the host with some characters in a register or two is as dirt simple of a console as you can get. It would be very easy to improve the user experience here if there were a: tdx_puts("uh oh"); interface. It's a shame if it didn't get done by now. I asked for it years ago. And, yeah, I know it wouldn't help us in this precise situation because earlyprintk doesn't work yet. But, it *would* be one of those really, really early bitbanging-style consoles that _could_ be in use very, very early if the printk() infrastructure could take advantage of it. > We can move it earlier into decompresser which has different earlyprintk > implementation. Not sure if it worth this. What do you think? There's the puts()/printf() gunk that's really early like in validate_cpu(). Is that what you were thinking of?