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 675F537BE94; Tue, 5 May 2026 11:24:12 +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=1777980254; cv=none; b=HxuLkJcqITtIIZ8mdlkkU70lGlRSjd0d29Xf9P3goEoUGgIRLZZtGUYE7JUe0UZr1/hl/YP586fImMIlqfrm3/kMzr2T7X7GOIGTBdI6iW0M1NnWeAiO1UPtv+y1o/quS9UyP959fMOas1yFGMK2PTG4Hxme8aiv9oTAT2iOTms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777980254; c=relaxed/simple; bh=rpFiR+vdDI9Jens/ZbxMoPcIN0EOhZWaI6j1ExASF3s=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Os5dmeHhJpEhETxJg9Grmv3iXpYrUb7hzZM4zmSp/NBljNw0zdPQ+zMDvvitCX7bHzjIuEVAQbTrtfzT2dZeR3S/OMjpbgjqhwFjyXOIe2495Ubld/17k9U/UDZei2tXwNQrlup5aYmIooCCFCSmpJpVwb8e42aCkmvPNqaycks= 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=AJgMQSFD; 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="AJgMQSFD" 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 5897228FA; Tue, 5 May 2026 04:24:06 -0700 (PDT) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BA9053F836; Tue, 5 May 2026 04:24:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777980251; bh=rpFiR+vdDI9Jens/ZbxMoPcIN0EOhZWaI6j1ExASF3s=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=AJgMQSFDNLMFgJA4Rzy1bbY/vHgUcHNpArSUbowzeCwli1B7rVkpkZZs1BGfgX732 +XBfmGkS6nOSdYI4mbPPb+fZzJlXD7dRK0ciA0kQHQXyJQZGkjVdkX+BAjQSrdaL3h eLmFNHwS+Nl9RprkGrMTy2tVPIXodezJ1WNWhwh4= Message-ID: <9dd2b09b-cfb1-40e5-9fdd-1e004ad784c0@arm.com> Date: Tue, 5 May 2026 12:24:07 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [RFC PATCH 0/3] initalise ff-a after finalising pKVM To: Yeoreum Yun 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 References: <20260505095409.1948371-1-yeoreum.yun@arm.com> <8942c12e-6315-493e-98c5-d55f4e6341f4@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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? Thanks, Ben > > [...] > > Thanks. >