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 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.lore.kernel.org (Postfix) with ESMTPS id E591BC636CC for ; Thu, 16 Feb 2023 18:33:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Wn5GqFm3wSIrzxjcRyMmq4y1MO4X80rJWDImJ9BZn4Y=; b=lEZlwyRxyvt0Jj qJD0ZTLaHmC33Ca/f7UpDr04dXDfn+mfh3V2iZps21TnwPs2wRmWybXcv5lcYD8AKLOetxztWYlVx +DbOsgczSLn3WEbiVG3LY+47G/3BVX9TCL0Cb5twLcKC75CSdh2LJurXymmE6dyPxq/5hrETobH1m 6mazGSBlgnfRiwPoN7qHZCnLqtNlhOVsNt6dxtMGwTNuNbrzhMeqTEPYI0eW+LfNOBRkfHWLm2U8j I6owsLC7ht2qUN+uRLjsmjLBPxh8DnlNrjaPI+riC4Pj10gzaLaRPpfg6pRRKUNLS495DUbs2L/fl Z0fbil5uQ45QDJOQ305A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSj43-00BXXX-Jw; Thu, 16 Feb 2023 18:33:03 +0000 Received: from mga03.intel.com ([134.134.136.65]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pSj3y-00BXVq-AH for kexec@lists.infradead.org; Thu, 16 Feb 2023 18:33:02 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1676572378; x=1708108378; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Zfp7UkFHu3uObj2djITRWHGzW92NYU2r9XQ28CZ8TzM=; b=SwXCSo3nUZaa3lLUP6dslVrl+1rKK0bMtesO0/WcS48H1OKTpAHar7vc HNsEw8V9OyWuLqoKyxVwloo0MGz6fpWRSGprQLKHMq/LtCeBWrcOvGgBc gIzSlusioO/2BnHkZfYy91Ud78X4CRXs+NOZMPnEcEclzdWvioeL1pvjT HyHL4Kx4whxApPVpVJt2r3AOds91PF4FNmwAADjeeqYSvn3Eu4Z3sH/VM CLTM0Aa6QfJDOSNJF4IqMTb9s5ydrCrf/2GAIoC0l41a1VGPm+wWTRVaF 4dxNLTO3FfQauNdHTjxNXRAJbP9oenxQJiYEhuziPGeyJgm/A2FIrrk79 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10623"; a="333998541" X-IronPort-AV: E=Sophos;i="5.97,302,1669104000"; d="scan'208";a="333998541" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Feb 2023 10:32:54 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10623"; a="670255337" X-IronPort-AV: E=Sophos;i="5.97,302,1669104000"; d="scan'208";a="670255337" Received: from bjelliot-mobl1.amr.corp.intel.com (HELO [10.209.100.192]) ([10.209.100.192]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Feb 2023 10:32:47 -0800 Message-ID: <3ecc4208-9165-bc7c-d71b-2b93571f42af@intel.com> Date: Thu, 16 Feb 2023 10:32:47 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH 0/2] Kexec enabling in TDX guest Content-Language: en-US To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Borislav Petkov , Kuppuswamy Sathyanarayanan , Thomas Gleixner , Isaku Yamahata , x86@kernel.org, linux-coco@lists.linux.dev, kexec@lists.infradead.org, linux-kernel@vger.kernel.org References: <20230213234836.3683-1-kirill.shutemov@linux.intel.com> <65fc95bb-5ad9-b589-d6a4-762289b3f6bc@intel.com> <20230216181230.3jn5hebv3xkdivbx@box.shutemov.name> From: Dave Hansen In-Reply-To: <20230216181230.3jn5hebv3xkdivbx@box.shutemov.name> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230216_103258_405266_C68C77B0 X-CRM114-Status: GOOD ( 11.20 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 2/16/23 10:12, Kirill A. Shutemov wrote: > On Thu, Feb 16, 2023 at 09:50:32AM -0800, Dave Hansen wrote: >> On 2/13/23 15:48, Kirill A. Shutemov wrote: >>> The patch brings basic enabling of kexec in TDX guests. >>> >>> By "basic enabling" I mean, kexec in the guests with a single CPU. >>> TDX guests use ACPI MADT MPWK to bring up secondary CPUs. The mechanism >>> doesn't allow to put a CPU back offline if it has woken up. >>> >>> We are looking into this, but it might take time. >> This is simple enough. But, nobody will _actually_ use this code as-is, >> right? What's the point of applying it now? > Why nobody? Single CPU VMs are not that uncommon. Here's one data point: the only "General Purpose" ones I see AWS offering are Haswell era: https://aws.amazon.com/ec2/instance-types/ That _might_ be because of concerns about SMT side-channel exposure on anything newer. So, we can argue about what "uncommon" means. But, a minority of folks care about 1-cpu VMs. Also, a separate minority of folks care about kexec(). I'm worried that the overlap between the two will be an *OVERWHELMING* minority of folks. In other words, so few people will use this code that it'll just bitrot. I'm looking for compelling arguments why mainline should carry this. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec