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Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wKDN8-0000000DGJe-0gFl for linux-arm-kernel@lists.infradead.org; Tue, 05 May 2026 10:51:28 +0000 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 48921293B; Tue, 5 May 2026 03:51:17 -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 616003F763; Tue, 5 May 2026 03:51:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777978282; bh=yZGdbNWnv9AoNALmOOSMNuAEp4erSnU4LfuZqIJ1ueY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kziGBvU37OCRkjSk94kK2RNrvOTI7j03WaTu6gqQKEYis1J9WqfWuFXKEQJJXQ3Pm f3Zcu2a1JWetSs8y/sR5hkYbTl2r17K+YEucmsp1K+ITQlE3tCjIacm9n5SXGQ/Cxg qGjQ/dVMccsdc4nV7gwWQ+Ox028n1F5B3j4bRdRY= Date: Tue, 5 May 2026 11:51:16 +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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8942c12e-6315-493e-98c5-d55f4e6341f4@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260505_115126_626100_2DE3FCED X-CRM114-Status: GOOD ( 32.30 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. 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? > > > even before FF-A version negotiation since handler’s purpose seems to hook > > certain memory operations, and DIRECT_MSG_REQ has been available > > since FF-A specification v1.0. > > > > Any feedback or alternative suggestions would be appreciated! > > > > Link: https://lore.kernel.org/all/20260422162449.1814615-1-yeoreum.yun@arm.com/ [0] > > > > Yeoreum Yun (3): > > arm64: KVM: defer kvm_init() to finalise_pkvm() when pKVM is enabled > > firmware: arm_ffa: initialise ff-a after finalising pKVM > > initialisation > > security: integrity: call load_uefi_certs() at late_initcall_sync > > > > arch/arm64/kvm/arm.c | 8 +- > > arch/arm64/kvm/pkvm.c | 15 ++- > > drivers/firmware/arm_ffa/bus.c | 125 +++++++++++++++++- > > drivers/firmware/arm_ffa/common.h | 13 +- > > drivers/firmware/arm_ffa/driver.c | 21 ++- > > drivers/firmware/arm_ffa/smccc.c | 2 +- > > security/integrity/platform_certs/load_uefi.c | 2 +- > > 7 files changed, 166 insertions(+), 20 deletions(-) > > > > > > base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32 > -- Sincerely, Yeoreum Yun