From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9D9872D29C8; Thu, 25 Jun 2026 13:16:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782393407; cv=none; b=UQbyxIQYHkQ16+yTr5OO6kvoLWGzV+nbJKX7RpYvAQRhT/e1g9y5raEkmrUjq97L7Ia928OcPsWCnvadjqITyjW6YLZdHK797wdquk1UIZcSaQQtCmofELab8/blykS4rSrD9YsBO25vdog5CqnNaE56N4XlxNcQWcgL4VwH2vU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782393407; c=relaxed/simple; bh=r1Ujuj9y+OW8+P3gB0lSbn9j4JqYBEGFNwx5Q0U6skE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pRq59vJy9UbGSIyGAshibX79A6sYlxww8jb5Ebzi8VJvKyfSE1HyzT/0FNSZ+85dIaswxLLXN4L3/v4xTtHwltCsgkbJVlLg77FxYrgV4EHLVDI8w9WLoL3lbe1PI4lITqOhZOMUXjw3GwSsxOypxlUQpbJNWvzl26tYKbQzkZc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V7RNqNMt; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="V7RNqNMt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1BFD1F000E9; Thu, 25 Jun 2026 13:16:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782393406; bh=zyakJI5GD+PPIi44Smd0pGSoFVHMmc9YUMca9wIzM/Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=V7RNqNMtT8EQbl8j+mRtB5l3CkkFA8q8eOgYGPMBzwPHRtjhPy+Qwsk2m+rqWkrPq iWQPr1L5YtnwkHmC7gUyUUIcQ3j9m+4DrqD62tOxbXA5j8kc75G56f1q84kfIsoB4E LF+M2nGWlSOge7hXVNobOpw9S7KSCZ67i6c38EjryAbDGHgBVtHTM16eT27NAypvm7 HqcWL+hf6ZwajOgUBiy0KDluFFEQYUeSAGvekRvwDbjMrG0b6RKr8VlH+o5Btoyh85 pv0jGp9g6o9nNvSDUYQmf03mMdKYnugjiZvA8VnHwh+mwks4Z25LYWQC/PZ1teCmBk NXx5wLl6LtSKg== Date: Thu, 25 Jun 2026 14:16:40 +0100 From: Will Deacon To: Sebastian Ene Cc: catalin.marinas@arm.com, maz@kernel.org, oupton@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, vdonnefort@google.com, yuzenghui@huawei.com Subject: Re: [PATCH v5 1/7] KVM: arm64: Enforce strict SBZ checks in the FF-A proxy Message-ID: References: <20260623115354.632361-1-sebastianene@google.com> <20260623115354.632361-2-sebastianene@google.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=us-ascii Content-Disposition: inline In-Reply-To: <20260623115354.632361-2-sebastianene@google.com> Hi all, On Tue, Jun 23, 2026 at 11:53:48AM +0000, Sebastian Ene wrote: > Introduce a helper method ffa_check_unused_args_sbz to enforce strict > arguments checking when the hypervisor acts as a relayer between the > host and Trustzone. > > Signed-off-by: Sebastian Ene > Reviewed-by: Vincent Donnefort > --- > arch/arm64/kvm/hyp/nvhe/ffa.c | 54 +++++++++++++++++++++++++++++++++++ > 1 file changed, 54 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c > index 1af722771178..78bb043b33ee 100644 > --- a/arch/arm64/kvm/hyp/nvhe/ffa.c > +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c > @@ -71,6 +71,20 @@ static u32 hyp_ffa_version; > static bool has_version_negotiated; > static hyp_spinlock_t version_lock; > > +static bool ffa_check_unused_args_sbz(struct kvm_cpu_context *ctxt, int first_reg) > +{ > + DECLARE_REG(u32, func_id, ctxt, 0); > + int reg, end_reg; > + > + end_reg = ARM_SMCCC_IS_64(func_id) ? 17 : 7; > + for (reg = first_reg; reg <= end_reg; reg++) { > + if (cpu_reg(ctxt, reg)) > + return true; > + } > + > + return false; > +} Seb and I tried taking this for a spin on some Android devices and, sadly, it leads to fireworks. The reason is that the FF-A spec quietly changed the list of unused parameter registers for 64-bit SMCs from v1.1 to v1.2 of the spec so that pre-existing calls were affected. For example, in v1.1 a 64-bit RXTX_MAP only has x4-x7 as MBZ, whereas in v1.2 the same call has x4-x17 as SBZ. We can follow the spec by predicating the additional check on the FF-A version being >= 1.2, but I'm not hopeful that existing drivers are compliant. I also suggest moving this patch to the end of the series in case we need to revert it. Cheers, Will