From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 725743246E8; Tue, 5 May 2026 11:33:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777980817; cv=none; b=WB1osZk++vbpS4SOm4XyJQ82GACUkeYCYyYXVAYOlPCcC1i9NKgIE+LiB+dd+c3qGHiZJKhBW+7dqSNDb/bNUdjrLfu/AEd27JXdRKypwqygHVhICQcUewq5xeJCYTDaaGznMXpnVO6pAG+w66Td3i/0VzpEz9/H5BXWG+T58oQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777980817; c=relaxed/simple; bh=+DyxopJqusF4nqX/vk76jN9/BMcxqhGKLl2pzrxql/o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=la+UxRiFqw0cS0Di+GpEi5bYtZEcVOFh00xHPZ0jFtSkQ6svkNAJXUdmCtpC+nRKiQGMhlYt5gyfZGUdosukTLvaGwmdj/aVwPYHc3loqTZa3BubK/yLcM8HzDfVDUHdtBtaI5WbhXBk9W5MlEjsXSr+NFop8VNUeiv0YWWbWVM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=PgllxUh/; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="PgllxUh/" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 72A3C28FA; Tue, 5 May 2026 04:33:29 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.1.197.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 153CD3F836; Tue, 5 May 2026 04:33:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777980814; bh=+DyxopJqusF4nqX/vk76jN9/BMcxqhGKLl2pzrxql/o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PgllxUh/+rurhDG4ZVlwOUR1EM62YW/bBUT1vPkk63CPw+4peA3MGi7r9FWwhkxdL csld+6LN4XrOrnBZAEG1WbKfU9RqC983hgOWrbsOs6u5R1rcsp1oQnVKqpRIZPX4/7 Wrz6e8KbA3Y/ywZQtIDwzL+0NQ9iz/5L/asRAqhU= Date: Tue, 5 May 2026 12:33:28 +0100 From: Yeoreum Yun To: Ben Horgan Cc: linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, jarkko@kernel.org, zohar@linux.ibm.com, roberto.sassu@huawei.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, sudeep.holla@kernel.org Subject: Re: [RFC PATCH 0/3] initalise ff-a after finalising pKVM Message-ID: References: <20260505095409.1948371-1-yeoreum.yun@arm.com> <8942c12e-6315-493e-98c5-d55f4e6341f4@arm.com> <9dd2b09b-cfb1-40e5-9fdd-1e004ad784c0@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9dd2b09b-cfb1-40e5-9fdd-1e004ad784c0@arm.com> > Hi Levi, > > On 5/5/26 12:16, Yeoreum Yun wrote: > >> Hi Ben, > >> > >>> Hi Levi, > >>> > >>> On 5/5/26 10:54, Yeoreum Yun wrote: > >>>> This patch is split out from the patchset [0] -- > >>>> fix FF-A call failure with pKVM when the FF-A driver is built-in, > >>>> specifically the IMA-related part. > >>>> > >>>> When pKVM is enabled, the FF-A driver must be initialised after pKVM. > >>>> Otherwise, pKVM cannot negotiate the FF-A version or obtain the RX/TX > >>>> buffer information, leading to failures in FF-A calls. > >>>> > >>>> Currently, pKVM initialisation completes at device_initcall_sync, > >>>> while ffa_init() runs at the device_initcall level. > >>>> > >>>> So far, linker deployes kvm_arm_init() before ffa_init(), and SMCs can > >>>> still be trapped even before finalise_pkvm() is invoked. > >>>> As a result, this issue has not been observed. > >>>> > >>>> However, relying on above stuff is fragile. > >>>> Therefore, when pKVM is enabled, the FF-A infrastructure should be > >>>> initialised only after pKVM initialisation has been fully finalised. > >>>> > >>>> To achieve this, introduce an ffa_root_dev ("arm-ffa") and > >>>> a corresponding driver to defer initialisation of the FF-A infrastructure > >>>> until pKVM initialisation is complete, and to defer probing of all FF-A devices until then > >>>> when pKVM is enabled. > >>>> > >>>> This patch is based on v7.1-rc2 > >>>> > >>>> Question: > >>>> > >>>> FF-A initialisation can occur at late_initcall. Because it may be deferred, > >>>> some FF-A requests cannot be serviced at that stage. > >>>> A typical example is the EFI runtime variable service using DIRECT_MSG_REQ. > >>>> > >>>> Depending on the platform, the EFI runtime variable service runs with StandaloneMm > >>>> and uses FF-A DIRECT_REQ. However, when pKVM is enabled, FF-A initialisation > >>>> may be deferred to late_initcall. In this case, load_uefi_certs() > >>>> can fail if it is invoked before the FF-A driver is initialised > >>>> via deferred_probe_initcall(). > >>>> > >>>> Moving load_uefi_certs() to late_initcall_sync, as in the third patch, > >>>> seems not to have any problem since late_initcall and > >>>> late_initcall_sync are both of do_basic_setup() and it's before loading > >>>> init process. However, it is still unclear whether > >>>> it would be better to allow DIRECT_MSG_REQ in kvm_host_ffa_handler() > >>> > >>> The spec doesn't allow this. Looking at DEN0077A 1.2 REL0: > >>> > >>> Section 13.2.2 says: > >>> > >>> "If they are compatible, it enables them to determine which Framework functionalities can be used. Hence, negotiation of > >>> the version must happen before an invocation of any other FF-A ABI." > >>> > >>> and a bit further down > >>> > >>> "Once the caller invokes any FF-A ABI other than FFA_VERSION, the version negotiation phase is complete." > >>> > >>> I would have thought that an SP would only go into the waiting state once the version negotiation is done. > >> > >> I mean the negotiation between hypervisor and ff-a driver. > >> actually the version negotiation is done with SPMC in > >> hyp_ffa_init() but the negotiaion between hypervisor and ff-a driver > >> just choose the lower version between version requested from ff-a driver > >> and negotiated version with hypervisor and SPMC. > > > > Sorry. re-parse the word, not choose "re-negotiate" when > > FF-A driver request lowever version. > > > >> > >> So, the version negotiation is already done with SPMC > >> but with FF-A driver with hypervisor is not yet. > >> However, DIRECT_MSG_REQ has supported from v1.0 > >> In this situation, is there any reason not to send DIRECT_REQ_MSG? > > > > IOW, question is that some of ff-a request can be allowed > > before version negotiation with FF-A driver but > > using negotiated version via hyp_ffa_init() first or not. > > I don't think so. Isn't it more a continuation of the negotiation rather than a re-negotiation? Might be. However, in the case I mentioned, I’m asking because it’s somewhat unusual in that the FF-A request occurs without an “FF-A driver.” If the FF-A request goes through the FF-A driver, then as you said, it can reasonably be considered a continuation of the negotiation. But in this case, I was wondering whether it would be acceptable to introduce additional exception handling for situations where an FF-A request occurs without the FF-A driver. >From that perspective, even if the FF-A request does not go through the FF-A driver, it would ultimately still have to wait until the FF-A driver initialization is complete. So my question was whether certain operations could be handled as exceptions in such cases. Thanks. -- Sincerely, Yeoreum Yun