Re: [PATCH v6 4/5] KVM: arm64: Bump the supported version of FF-A to 1.2

[Marc Zyngier <maz@kernel.org>]

On Fri, 27 Jun 2025 08:12:28 +0100,
Per Larsen via B4 Relay <devnull+perlarsen.google.com@kernel.org> wrote:
> 
> From: Per Larsen <perlarsen@google.com>
> 
> FF-A version 1.2 introduces the DIRECT_REQ2 ABI. Bump the FF-A version
> preferred by the hypervisor as a precursor to implementing the 1.2-only
> FFA_MSG_SEND_DIRECT_REQ2 and FFA_MSG_SEND_RESP2 messaging interfaces.
> 
> We must also use SMCCC 1.2 for 64-bit SMCs if hypervisor negotiated FF-A
> 1.2, so ffa_set_retval is updated and a new function to call 64-bit smcs
> using SMCCC 1.2 with fallback to SMCCC 1.1 is introduced.
> 
> Update ffa_call_supported to mark FF-A 1.2 interfaces as unsupported
> lest they get forwarded.
> 
> Co-developed-by: Ayrton Munoz <ayrton@google.com>
> Signed-off-by: Ayrton Munoz <ayrton@google.com>
> Signed-off-by: Per Larsen <perlarsen@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 14 ++++++++++----
>  include/linux/arm_ffa.h       |  1 +
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 5fd6474d96ae4b90d99796ee81bb36373219afc4..d543d1f5ddd62fb15f8d39f4ff7d5bb0006da4a1 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -678,6 +678,12 @@ static bool ffa_call_supported(u64 func_id)
>  	case FFA_NOTIFICATION_SET:
>  	case FFA_NOTIFICATION_GET:
>  	case FFA_NOTIFICATION_INFO_GET:
> +	/* Unimplemented interfaces added in FF-A 1.2 */
> +	case FFA_MSG_SEND_DIRECT_REQ2:
> +	case FFA_MSG_SEND_DIRECT_RESP2:

Are those actually optional?

> +	case FFA_CONSOLE_LOG:
> +	case FFA_PARTITION_INFO_GET_REGS:
> +	case FFA_EL3_INTR_HANDLE:
>  		return false;
>  	}
>  
> @@ -734,7 +740,7 @@ static int hyp_ffa_post_init(void)
>  	if (res.a0 != FFA_SUCCESS)
>  		return -EOPNOTSUPP;
>  
> -	switch (res.a2) {
> +	switch (res.a2 & FFA_FEAT_RXTX_MIN_SZ_MASK) {

You should also check that the MBZ fields are still 0. Ideally, you'd
also do that with x3.

>  	case FFA_FEAT_RXTX_MIN_SZ_4K:
>  		min_rxtx_sz = SZ_4K;
>  		break;
> @@ -931,7 +937,7 @@ int hyp_ffa_init(void *pages)
>  
>  	arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
>  		.a0 = FFA_VERSION,
> -		.a1 = FFA_VERSION_1_1,
> +		.a1 = FFA_VERSION_1_2,
>  	}, &res);
>  	if (res.a0 == FFA_RET_NOT_SUPPORTED)
>  		return 0;
> @@ -952,10 +958,10 @@ int hyp_ffa_init(void *pages)
>  	if (FFA_MAJOR_VERSION(res.a0) != 1)
>  		return -EOPNOTSUPP;
>  
> -	if (FFA_MINOR_VERSION(res.a0) < FFA_MINOR_VERSION(FFA_VERSION_1_1))
> +	if (FFA_MINOR_VERSION(res.a0) < FFA_MINOR_VERSION(FFA_VERSION_1_2))
>  		hyp_ffa_version = res.a0;
>  	else
> -		hyp_ffa_version = FFA_VERSION_1_1;
> +		hyp_ffa_version = FFA_VERSION_1_2;
>  
>  	tx = pages;
>  	pages += KVM_FFA_MBOX_NR_PAGES * PAGE_SIZE;
> diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
> index 5bded24dc24fea8cdcbe42bf79c7c025c3fa5f4b..c0dd6183d956043192114a522b7eef465e7078ac 100644
> --- a/include/linux/arm_ffa.h
> +++ b/include/linux/arm_ffa.h
> @@ -128,6 +128,7 @@
>  #define FFA_FEAT_RXTX_MIN_SZ_4K		0
>  #define FFA_FEAT_RXTX_MIN_SZ_64K	1
>  #define FFA_FEAT_RXTX_MIN_SZ_16K	2
> +#define FFA_FEAT_RXTX_MIN_SZ_MASK	3

nit: a mask is better expressed with GENMASK, making it obvious that
this is not just another value.

Thanks,

	M.

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