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[104.155.91.135]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-bf0522834dbsm1145247966b.27.2026.06.10.02.27.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jun 2026 02:27:03 -0700 (PDT) Date: Wed, 10 Jun 2026 10:26:59 +0100 From: Vincent Donnefort To: Sebastian Ene Cc: catalin.marinas@arm.com, maz@kernel.org, oupton@kernel.org, will@kernel.org, joey.gouly@arm.com, korneld@google.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, android-kvm@google.com, mrigendra.chaubey@gmail.com, perlarsen@google.com, suzuki.poulose@arm.com, yuzenghui@huawei.com Subject: Re: [PATCH v2 0/7] KVM: arm64: Forward FFA_NOTIFICATION* calls to TrustZone Message-ID: References: <20260608165549.1479409-1-sebastianene@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260608165549.1479409-1-sebastianene@google.com> On Mon, Jun 08, 2026 at 04:55:42PM +0000, Sebastian Ene wrote: > Remove the FFA_NOTIFICATION* calls from the blocklist used by the pKVM > FF-A proxy. This restriction was preventing the use of asynchronous > signaling mechanisms defined by the Arm FF-A specification to > communicate with the secure services. > While these calls are markes as optional, there is no reason why the > hypervisor proxy would block them because: > > 1. Host is the Sole Non-Secure Endpoint: The Host operates as the > only Non-Secure VM ID (VM ID 0) recognized by the Secure World. > Because all forwarded notifications are inherently attributed to > the Host by the SPMC, there is no risk of VM ID spoofing > originating from the Normal World. > > 2. No Memory Pointers or Addresses: The FFA_NOTIFICATION_* ABIs > operate strictly via register-based parameters, passing only > VM IDs, VCPU IDs, flags, and bitmaps. Because these calls do > not contain memory addresses, offsets, or pointers, forwarding > them doesn't pose a risk of memory-based confused deputy attack > (e.g., tricking the SPMC into overwriting protected memory). > > While the pKVM proxy behaves as a relayer, it doesn't currently have its > own FF-A ID(only the host has the ID 0). The behavior of the setup > flow is covered by the spec in the: '10.9 Notification support without > a Hypervisor'. As it is only a relayer. Is it really important to check SBZ arguments and fields on behalf of Trustzone? It doesn't feel it brings any security. If the host passes broken arguments, I don't believe this puts pKVM at risk. Does it? > > --- > Changes in v2: > - enforce the MBZ/SBZ fields > - split the calls into separate patches > - rebase on 7.1-rc7 > > Link to v1: > https://lore.kernel.org/all/20260501114447.2389222-2-sebastianene@google.com/ > > Sebastian Ene (7): > KVM: arm64: Support FFA_NOTIFICATION_BITMAP_CREATE in host handler > KVM: arm64: Support FFA_NOTIFICATION_BITMAP_DESTROY in host handler > KVM: arm64: Support FFA_NOTIFICATION_BIND in host handler > KVM: arm64: Support FFA_NOTIFICATION_UNBIND in host handler > KVM: arm64: Support FFA_NOTIFICATION_SET in host handler > KVM: arm64: Support FFA_NOTIFICATION_GET in host handler > KVM: arm64: Support FFA_NOTIFICATION_INFO_GET in host handler > > arch/arm64/kvm/hyp/nvhe/ffa.c | 190 ++++++++++++++++++++++++++++++++-- > 1 file changed, 182 insertions(+), 8 deletions(-) > > -- > 2.54.0.1064.gd145956f57-goog >