Re: [RFC PATCH 4/4] firmware: arm_ffa: check pkvm initailised when initailise ffa driver

[Marc Zyngier <maz@kernel.org>]

On Fri, 17 Apr 2026 18:57:59 +0100,
Yeoreum Yun <yeoreum.yun@arm.com> wrote:
> 
> When pKVM is enabled, the FF-A driver must be initialized after pKVM.
> Otherwise, pKVM cannot negotiate the FF-A version or
> obtain RX/TX buffer information, leading to failures in FF-A calls.
> 
> During FF-A driver initialization, check whether pKVM has been initialized.
> If not, defer probing of the FF-A driver.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
> ---
>  arch/arm64/kvm/arm.c              |  1 +
>  drivers/firmware/arm_ffa/driver.c | 12 ++++++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 410ffd41fd73..0f517b1c05cd 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -119,6 +119,7 @@ bool is_kvm_arm_initialised(void)
>  {
>  	return kvm_arm_initialised;
>  }
> +EXPORT_SYMBOL(is_kvm_arm_initialised);

EXPORT_SYMBOL_GPL(), please.

> 
>  int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
>  {
> diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
> index 02c76ac1570b..2647d6554afd 100644
> --- a/drivers/firmware/arm_ffa/driver.c
> +++ b/drivers/firmware/arm_ffa/driver.c
> @@ -42,6 +42,8 @@
>  #include <linux/uuid.h>
>  #include <linux/xarray.h>
> 
> +#include <asm/virt.h>
> +
>  #include "common.h"
> 
>  #define FFA_DRIVER_VERSION	FFA_VERSION_1_2
> @@ -2035,6 +2037,16 @@ static int __init ffa_init(void)
>  	u32 buf_sz;
>  	size_t rxtx_bufsz = SZ_4K;
> 
> +	/*
> +	 * When pKVM is enabled, the FF-A driver must be initialized
> +	 * after pKVM initialization. Otherwise, pKVM cannot negotiate
> +	 * the FF-A version or obtain RX/TX buffer information,
> +	 * which leads to failures in FF-A calls.
> +	 */
> +	if (IS_ENABLED(CONFIG_KVM) && is_protected_kvm_enabled() &&
> +	    !is_kvm_arm_initialised())
> +		return -EPROBE_DEFER;
> +

That's still fundamentally wrong: pkvm is not ready until
finalize_pkvm() has finished, and that's not indicated by
is_kvm_arm_initialised().

	M.

-- 
Jazz isn't dead. It just smells funny.