From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) (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 3F8DF4403 for ; Tue, 9 Aug 2022 11:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660045896; x=1691581896; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=eDgcat5jz2gPDhDhIYJ5SQ3oYmJhT05bUBFYCgTExWE=; b=laTFrPr57ISmk0E4sHdlCBilhRhhuLIeLjaEzV+cjcQXFeLmwqf3LCUw uFedkMLWkRRlHlTkzP59iRDWh9TJFlCqrdiNNmPdlRvGBNw8mtFg2/XH2 NiIye3iSlQ1dYKihgHWBVkE1WogZTLRbcbKxzCjH1270fnXfd4ce3HfLg Cz5goIQKxSL2z1hRcJ1kDv6LTA1DnGH+DzLSSR18edQU3VPS/jHZ0lorb 33LlwP6IRCzRa4DcNC6hsV7QfP7x6vVZdJqWEz36ULXAOc0R8yDJXWe7N munDn82Ebx+Z/gOLrBcigoWxl/pYLJ/v25m4hh8reORP0qAc8W1PHHFZw g==; X-IronPort-AV: E=McAfee;i="6400,9594,10433"; a="277750685" X-IronPort-AV: E=Sophos;i="5.93,224,1654585200"; d="scan'208";a="277750685" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Aug 2022 04:51:35 -0700 X-IronPort-AV: E=Sophos;i="5.93,224,1654585200"; d="scan'208";a="747012231" Received: from labukara-mobl.ger.corp.intel.com (HELO box.shutemov.name) ([10.251.214.212]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Aug 2022 04:51:29 -0700 Received: by box.shutemov.name (Postfix, from userid 1000) id 7CAAF103886; Tue, 9 Aug 2022 14:54:27 +0300 (+03) Date: Tue, 9 Aug 2022 14:54:27 +0300 From: "Kirill A. Shutemov" To: Ard Biesheuvel Cc: Dave Hansen , Marc Orr , Borislav Petkov , Dionna Amalie Glaze , Peter Gonda , Andy Lutomirski , Sean Christopherson , Andrew Morton , Joerg Roedel , Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Varad Gautam , Dario Faggioli , Mike Rapoport , David Hildenbrand , Marcelo Cerri , tim.gardner@canonical.com, Khalid ElMously , philip.cox@canonical.com, the arch/x86 maintainers , Linux Memory Management List , linux-coco@lists.linux.dev, linux-efi , LKML , "Yao, Jiewen" Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory Message-ID: <20220809115427.bmkbap434oupinq2@box.shutemov.name> References: <22d54786-bc12-ecc5-2b37-cbaa56090aa8@intel.com> <20220809111436.kudwg2nprnnsfvuh@box.shutemov.name> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Aug 09, 2022 at 01:36:00PM +0200, Ard Biesheuvel wrote: > On Tue, 9 Aug 2022 at 13:11, Kirill A. Shutemov > wrote: > > > > On Sat, Jul 23, 2022 at 01:14:07PM +0200, Ard Biesheuvel wrote: > > > On Thu, 21 Jul 2022 at 19:13, Dave Hansen wrote: > > > > > > > > On 7/19/22 17:26, Marc Orr wrote: > > > > > - Dave's suggestion to "2. Boot some intermediate thing like a > > > > > bootloader that does acceptance ..." is pretty clever! So if upstream > > > > > thinks this FW-kernel negotiation is not a good direction, maybe we > > > > > (Google) can pursue this idea to avoid introducing yet another tag on > > > > > our images. > > > > > > > > I'm obviously speaking only for myself here and not for "upstream" as a > > > > whole, but I clearly don't like the FW/kernel negotiation thing. It's a > > > > permanent pain in our necks to solve a very temporary problem. > > > > > > EFI is basically our existing embodiment of this fw/kernel negotiation > > > thing, and iff we need it, I have no objection to using it for this > > > purpose, i.e., to allow the firmware to infer whether or not it should > > > accept all available memory on behalf of the OS before exiting boot > > > services. But if we don't need this, even better. > > > > FW/kernel negotiation does not work if there's a boot loader in the middle > > that does ExitBootServices(). By the time kernel can announce if it > > supports unaccepted memory there's nobody to announce to. > > > > Why would you want to support such bootloaders for TDX anyway? TDX > heavily relies on measured boot abstractions and other things that are > heavily tied to firmware. I don't understand it either. And, yet, there's demand for it. -- Kiryl Shutsemau / Kirill A. Shutemov