linux-kernel - Re: [PATCH 2/2] KVM: arm64: Allow only the specified FF-A calls to be forwarded to TZ

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Message-ID: <Zf45eDs8Bd1UQ94Z@linux.dev>
Date: Fri, 22 Mar 2024 19:07:52 -0700
From: Oliver Upton <oliver.upton@...ux.dev>
To: Sebastian Ene <sebastianene@...gle.com>
Cc: catalin.marinas@....com, james.morse@....com, jean-philippe@...aro.org,
	maz@...nel.org, qperret@...gle.com, qwandor@...gle.com,
	suzuki.poulose@....com, tabba@...gle.com, will@...nel.org,
	yuzenghui@...wei.com, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel-team@...roid.com
Subject: Re: [PATCH 2/2] KVM: arm64: Allow only the specified FF-A calls to
 be forwarded to TZ

On Fri, Mar 22, 2024 at 12:43:03PM +0000, Sebastian Ene wrote:
> The previous logic used a deny list to filter the FF-A calls. Because of
> this, some of the calls escaped the check and they were forwarded by
> default to Trustzone. (eg. FFA_MSG_SEND_DIRECT_REQ was denied but the 64
> bit version of the call was not).
> Modify the logic to use an allowlist and allow only the calls specified in
> the filter function to be proxied to TZ from the hypervisor.

I had discussed this with Will back when the feature was upstreamed and
he said there's a lot of off-label calls that necessitate a denylist
implementation. Has anything changed to give us confidence that we can
be restrictive, at least on the FF-A range?

-- 
Thanks,
Oliver