Re: [PATCH] KVM: arm64: Fix error checking for FFA_VERSION

[Marc Zyngier <maz@kernel.org>]

On Fri, 14 Nov 2025 11:11:53 +0000,
"=?utf-8?q?Kornel_Dul=C4=99ba?=" <korneld@google.com> wrote:
> 
> According to section 13.2 of the DEN0077 FF-A specification, when
> firmware does not support the requested version, it should reply with
> FFA_RET_NOT_SUPPORTED(-1). Table 13.6 specifies the type of the error
> code as int32.
> Currently, the error checking logic compares the unsigned long return
> value it got from the SMC layer, against a "-1" literal. This fails due
> to a type mismatch: the literal is extended to 64 bits, whereas the
> register contains only 32 bits of ones(0x00000000ffffffff).
> Consequently, hyp_ffa_init misinterprets the "-1" return value as an
> invalid FF-A version. This prevents pKVM initialization on devices where
> FF-A is not supported in firmware.

Is this statement accurate? I regularly boot KVM in protected mode in
environments that really cannot be suspected of implementing FF-A
(there is no EL3 to start with). And yet I don't see any failure of
the sort.

Please clarify the circumstances this is triggered.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.