From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-9102.amazon.com (smtp-fw-9102.amazon.com [207.171.184.29]) (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 8AB068624C; Thu, 21 Mar 2024 17:39:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=207.171.184.29 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711042788; cv=none; b=TsvahzagSWlq49EmIFRCgl4lx1NXI09ibktw/xc9diET+n4qSNwVsEzr1yCQ68MLHuc6FS0aLw27vLTdew12M8JRkU/BzlpknZAziYxoXS4TkFoEkCMzSRY5NLH4lrcaF6kjpc8pgqe1zbiZF4zfBmMEbidHRsXpPHimDrHzMQI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711042788; c=relaxed/simple; bh=tmVyl3CnV/a8ywSLGoP9rsnHV/1ICdCewlLv8W7cRX4=; h=Subject:Message-ID:Date:MIME-Version:To:CC:References:From: In-Reply-To:Content-Type; b=L4MYEzDeo+oWLsluX6bSgd7z1vX6RhraXBOLY0M9+IJVwNHhrD2a7Ut4c6kp3iMrVF2S3rTVoe7oGh25Y/FyOQ8S+sE+KRH06IJUXeCOptAENHbFu1eQ5oERoQu30mg247DOiIw2ObdG/MmPtOleuc53mbN2NkPtl4ci/ctKklc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk; spf=pass smtp.mailfrom=amazon.co.uk; dkim=pass (1024-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b=twhwCJ4M; arc=none smtp.client-ip=207.171.184.29 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.co.uk header.i=@amazon.co.uk header.b="twhwCJ4M" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.co.uk; i=@amazon.co.uk; q=dns/txt; s=amazon201209; t=1711042786; x=1742578786; h=message-id:date:mime-version:to:cc:references:from: in-reply-to:content-transfer-encoding:subject; bh=Y2m0HUIoPsV3lCWkx5c13P3hII6BgfumgnVO7r8vV/0=; b=twhwCJ4MOi1AdIEx/qlHJTs6nIanHZjex7NMfjF8GgPe8U6mWCflP6IM Z2YBiThp43iy4TsqUp+fFQlcxSOPKhq/XSS2ELeYw1m6DacFPVF12ImqT g28Ucu6vvGRIzOoYAGYk5iY1LwMYCheDk/LXF1lVwtF1vRxkr25KcjlXl Q=; X-IronPort-AV: E=Sophos;i="6.07,143,1708387200"; d="scan'208";a="405714813" Subject: Re: [PATCH v1 0/4] virt: vmgenid: Add devicetree bindings support Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.25.36.214]) by smtp-border-fw-9102.sea19.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Mar 2024 17:39:39 +0000 Received: from EX19MTAEUB001.ant.amazon.com [10.0.10.100:51553] by smtpin.naws.eu-west-1.prod.farcaster.email.amazon.dev [10.0.24.234:2525] with esmtp (Farcaster) id 07620b8e-e807-42d8-ae98-352d02494533; Thu, 21 Mar 2024 17:39:38 +0000 (UTC) X-Farcaster-Flow-ID: 07620b8e-e807-42d8-ae98-352d02494533 Received: from EX19D036EUC002.ant.amazon.com (10.252.61.191) by EX19MTAEUB001.ant.amazon.com (10.252.51.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.28; Thu, 21 Mar 2024 17:39:38 +0000 Received: from [192.168.15.25] (10.106.82.17) by EX19D036EUC002.ant.amazon.com (10.252.61.191) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.28; Thu, 21 Mar 2024 17:39:32 +0000 Message-ID: Date: Thu, 21 Mar 2024 17:39:28 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: Rob Herring , David Woodhouse CC: Krzysztof Kozlowski , Sudan Landge , , , , , , , , , , , , , , benh References: <20240319143253.22317-1-sudanl@amazon.com> <23692c07-98bd-477d-b244-bba14c50352c@linaro.org> <38aad6c0e698c8e804694276d1762d61f2068ce8.camel@infradead.org> <20240320161531.GA1810860-robh@kernel.org> <60404403932a984d1f75d111ff53b9053af03579.camel@infradead.org> <20240321133250.GA1600070-robh@kernel.org> From: "Landge, Sudan" In-Reply-To: <20240321133250.GA1600070-robh@kernel.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: EX19D044UWB002.ant.amazon.com (10.13.139.188) To EX19D036EUC002.ant.amazon.com (10.252.61.191) On 21/03/2024 13:32, Rob Herring wrote: > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > > > On Wed, Mar 20, 2024 at 04:55:45PM +0000, David Woodhouse wrote: >> On Wed, 2024-03-20 at 11:15 -0500, Rob Herring wrote: >>> On Wed, Mar 20, 2024 at 01:50:43PM +0000, David Woodhouse wrote: >>>> On Tue, 2024-03-19 at 16:24 +0100, Krzysztof Kozlowski wrote: >>>>> On 19/03/2024 15:32, Sudan Landge wrote: >>>>>> This small series of patches aims to add devicetree bindings support for >>>>>> the Virtual Machine Generation ID (vmgenid) driver. >>>>>> >>>>>> Virtual Machine Generation ID driver was introduced in commit af6b54e2b5ba >>>>>> ("virt: vmgenid: notify RNG of VM fork and supply generation ID") as an >>>>>> ACPI only device. >>>>>> We would like to extend vmgenid to support devicetree bindings because: >>>>>> 1. A device should not be defined as an ACPI or DT only device. >>> >>> This (and the binding patch) tells me nothing about what "Virtual >>> Machine Generation ID driver" is and isn't really justification for >>> "why". >> >> It's a reference to a memory area which the OS can use to tell whether >> it's been snapshotted and restored (or 'forked'). A future submission >> should have a reference to something like >> https://www.qemu.org/docs/master/specs/vmgenid.html or the Microsoft >> doc which is linked from there. > > That doc mentions fw_cfg for which we already have a binding. Why can't > it be used/extended here? QEMU has support for vmgenid but even they do not pass vmgenid directly to the guest kernel using fw_cfg. QEMU passes the vmgenid/UUID via fw_cfg to an intermediate UEFI firmware. This UEFI firmware, running as a guest in QEMU, reads the UUID from fw_cfg and creates ACPI tables for it. The UEFI firmware then passes the UUID information to the guest kernel via ACPI. This approach requires yet another intermediary which is UEFI firmware and adds more complexity than ACPI for minimalist hypervisors that do not have an intermediate bootloader today. > > Rob > > [1] https://www.kernel.org/doc/Documentation/devicetree/bindings/firmware/qemu%2Cfw-cfg-mmio.yaml