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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 4530CC7115B for ; Wed, 18 Jun 2025 07:29:10 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1018904.1395776 (Exim 4.92) (envelope-from ) id 1uRnE8-0003ro-6V; Wed, 18 Jun 2025 07:28:56 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1018904.1395776; Wed, 18 Jun 2025 07:28:56 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uRnE8-0003rh-3j; Wed, 18 Jun 2025 07:28:56 +0000 Received: by outflank-mailman (input) for mailman id 1018904; Wed, 18 Jun 2025 07:28:54 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1uRnE6-0003rZ-Sr for xen-devel@lists.xenproject.org; Wed, 18 Jun 2025 07:28:54 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.96) (envelope-from ) id 1uRnE6-007n1S-0e; Wed, 18 Jun 2025 07:28:54 +0000 Received: from [2a02:8012:3a1:0:64b5:81ad:1f26:5fcb] by xenbits.xenproject.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1uRnE5-009N5a-37; Wed, 18 Jun 2025 07:28:54 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID; bh=sGZjI4tbZbPBWUj9naF9XCrtdWBwG8WfLSjdxottyYc=; b=YSO8a4yGan0zatsEnxsEgW+26q FQuKLLu6M14uK0c/2VcvqxqbUc2Ae1IKiAML9lbCNxqsLltG905mlypAXaE2gyCemJAkCR8nntEJL k/lgEHsruBAJ0yts2pEoiuigfUe1F6oBtW/JSCIWenlOvDnygwTCsk/EQ7LTdpIMPspw=; Message-ID: <13d95459-ea77-46ea-84e4-cccece4cd496@xen.org> Date: Wed, 18 Jun 2025 08:28:51 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v4 6/8] xen/arm: scmi: introduce SCI SCMI SMC multi-agent driver Content-Language: en-GB To: Oleksii Moisieiev , "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Anthony PERARD , Bertrand Marquis , Jan Beulich , Juergen Gross , Michal Orzel , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , Volodymyr Babchuk , Grygorii Strashko References: <318044ae12f13b6b297b3f5fda577a1a6cd143da.1747669845.git.oleksii_moisieiev@epam.com> From: Julien Grall In-Reply-To: <318044ae12f13b6b297b3f5fda577a1a6cd143da.1747669845.git.oleksii_moisieiev@epam.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Oleksii, On 19/05/2025 16:50, Oleksii Moisieiev wrote: > This patch introduces SCI driver to support for ARM EL3 Trusted Firmware-A > (TF-A) which provides SCMI interface with multi-agnet support, as shown s/multi-agnet/multi-agent/ > below. > > +-----------------------------------------+ > | | > | EL3 TF-A SCMI | > +-------+--+-------+--+-------+--+-------++ > |shmem0 | |shmem1 | |shmem2 | |shmemX | > +-----+-+ +---+---+ +--+----+ +---+---+ > smc-id0 | | | | > agent0 | | | | > +-----v--------+---------+-----------+----+ > | | | | | > | | | | | > +--------------+---------+-----------+----+ > smc-id1 | smc-id2| smc-idX| > agent1 | agent2 | agentX | > | | | > +----v---+ +--v-----+ +--v-----+ > | | | | | | > | Dom0 | | Dom1 | | DomX | > | | | | | | > | | | | | | > +--------+ +--------+ +--------+ > > The EL3 SCMI multi-agent firmware expected to provide SCMI SMC/HVC shared > memory transport for every Agent in the system. > > The SCMI Agent transport channel defined by pair: > - smc-id: SMC/HVC id used for Doorbell > - shmem: shared memory for messages transfer, Xen page aligned, > p2m_mmio_direct_nc. It is not clear why we nention Xen page aligned and p2m_mmio_direct_nc. Is this multi-agent protocol tied to Xen? That said... p2m_mmio_direct_nc is a type used in the stage 2 page-tables to indicate how we restrict access from the domain. The resulting memory attribute will be a combination of stage-1 + stage-2. In the future, we may decide to use FWB which will allow Xen to force a specific memory attribute. This is also purely internal decision. In the documentation, you should spell out the memory attribute that should be used. From the discussion on this patch, it is still unclear whether the region should be mapped as Device nGnRE or normal memory non-cacheabl. Cheers, -- Julien Grall