From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-80009.amazon.com (smtp-fw-80009.amazon.com [99.78.197.220]) (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 55D43286281; Wed, 19 Feb 2025 13:55:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=99.78.197.220 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739973321; cv=none; b=sy2Bvpu09F93gTgztc5PISLjOUv2Nxuiyqc3Gqn7KqttjQkbikeP1T2j7v2xRsE9YLEzlpG2aNQEcm1u1iUe6NfWQbB5tJQwGyXBguqDwff04KOYNLdQK7Hp0KnUgM/dKKXqhvgV1o2cUVhsvSsN0GeS+dMYJmBo0wmQTi3KyTw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739973321; c=relaxed/simple; bh=Rc0k2hXGgw1uh7x0JIX+uzUH8a98VI2YuRrPPA9zVIw=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=DAIrsQZroAIUf6tgFTrgIaov9/G/uZDgwK9Qv/WoF+dYKEWdO0jHqjhX1ZkKZC5kdPfMOvnopsriEL47YLkyyBReK9zkAiZf7AMpt02Ih4lSevHwgxdVsmuu83n85vCHgNYtRj5ykS6Nx2DBwn8vbPcq3KLCdv37anKjan1P7Wg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.de; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b=uVXB7M5c; arc=none smtp.client-ip=99.78.197.220 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="uVXB7M5c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1739973320; x=1771509320; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=57nPLxtLibpkK5qPp8QpRrsWkbDlQlqDET5gkkKYRG8=; b=uVXB7M5cyZLysMGuSVF/79vI9AyRNj63EwEGDaEnRaCPROiolv3BpNqm 0xQR3AhHvXUUzDeevCgpSke4aLW1VVOLgLx7o8kkBhNcxw6kOMi/3GULy DCkcnzkMyOdxO0GB8PPKWkEKl8gwp6BKnZTbf+5dY8dR31eN1dUtilv5i M=; X-IronPort-AV: E=Sophos;i="6.13,299,1732579200"; d="scan'208";a="173851478" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.25.36.210]) by smtp-border-fw-80009.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Feb 2025 13:55:18 +0000 Received: from EX19MTAUWA002.ant.amazon.com [10.0.38.20:64466] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.12.97:2525] with esmtp (Farcaster) id 109703bc-b166-4b29-a69a-d899c4750143; Wed, 19 Feb 2025 13:55:17 +0000 (UTC) X-Farcaster-Flow-ID: 109703bc-b166-4b29-a69a-d899c4750143 Received: from EX19D020UWC004.ant.amazon.com (10.13.138.149) by EX19MTAUWA002.ant.amazon.com (10.250.64.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1258.39; Wed, 19 Feb 2025 13:55:08 +0000 Received: from [0.0.0.0] (10.253.83.51) by EX19D020UWC004.ant.amazon.com (10.13.138.149) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Wed, 19 Feb 2025 13:55:00 +0000 Message-ID: Date: Wed, 19 Feb 2025 14:54:57 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO) To: Dave Young , Mike Rapoport CC: , Andrew Morton , Andy Lutomirski , Anthony Yznaga , Arnd Bergmann , Ashish Kalra , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Dave Hansen , David Woodhouse , Eric Biederman , Ingo Molnar , James Gowans , Jonathan Corbet , Krzysztof Kozlowski , Mark Rutland , Paolo Bonzini , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra , Pratyush Yadav , Rob Herring , Rob Herring , Saravana Kannan , Stanislav Kinsburskii , Steven Rostedt , Thomas Gleixner , Tom Lendacky , Usama Arif , Will Deacon , , , , , , References: <20250206132754.2596694-1-rppt@kernel.org> Content-Language: en-US From: Alexander Graf In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: EX19D041UWA003.ant.amazon.com (10.13.139.105) To EX19D020UWC004.ant.amazon.com (10.13.138.149) On 19.02.25 13:49, Dave Young wrote: > On Wed, 19 Feb 2025 at 15:32, Mike Rapoport wrote: >> On Mon, Feb 17, 2025 at 11:19:45AM +0800, RuiRui Yang wrote: >>> On Thu, 6 Feb 2025 at 21:34, Mike Rapoport wrote: >>>> == Limitations == >>>> >>>> Currently KHO is only implemented for file based kexec. The kernel >>>> interfaces in the patch set are already in place to support user space >>>> kexec as well, but it is still not implemented it yet inside kexec tools. >>>> >>> What architecture exactly does this KHO work fine? Device Tree >>> should be ok on arm*, x86 and power*, but how about s390? >> KHO does not use device tree as the boot protocol, it uses FDT as a data >> structure and adds architecture specific bits to the boot structures to >> point to that data, very similar to how IMA_KEXEC works. >> >> Currently KHO is implemented on arm64 and x86, but there is no fundamental >> reason why it wouldn't work on any architecture that supports kexec. > Well, the problem is whether there is a way to add dtb in the early > boot path, for X86 it is added via setup_data, if there is no such > way I'm not sure if it is doable especially for passing some info for > early boot use. Then the KHO will be only for limited use cases. Every architecture has a platform specific way of passing data into the kernel so it can find its command line and initrd. S390x for example has struct parmarea. To enable s390x, you would remove some of its padding and replace it with a KHO base addr + size, so that the new kernel can find the KHO state tree. Alex