Re: [PATCH v6 3/6] xen/arm: ffa: Introduce VM to VM support

[Julien Grall <julien@xxxxxxx>]

Hi Bertrand,

On 22/05/2025 16:08, Bertrand Marquis wrote:
> diff --git a/xen/arch/arm/tee/ffa_partinfo.c b/xen/arch/arm/tee/ffa_partinfo.c
> index dfa0b23eaf38..66ea1860e97a 100644
> --- a/xen/arch/arm/tee/ffa_partinfo.c
> +++ b/xen/arch/arm/tee/ffa_partinfo.c
> @@ -150,6 +150,67 @@ out:
>       return ret;
>   }
>   
> +static int32_t ffa_get_vm_partinfo(uint32_t *vm_count, void *dst_buf,
> +                                   void *end_buf, uint32_t dst_size)
> +{
> +    struct ffa_ctx *curr_ctx = current->domain->arch.tee;
> +    struct ffa_ctx *dest_ctx, *tmp;
> +    uint32_t count = 0;
> +
> +    /*
> +     * There could potentially be a lot of VMs in the system and we could
> +     * hold the CPU for long here.
> +     * Right now there is no solution in FF-A specification to split
> +     * the work in this case.
> +     * TODO: Check how we could delay the work or have preemption checks.
> +     */
> +    list_for_each_entry_safe(dest_ctx, tmp, &ffa_ctx_head, ctx_list)
Looking at this code again, I am a bit puzzled why we don't seem to take 
any lock and use list_for_each_entry_safe().
I was under the impression that list_for_each_entry_safe() is used if we
delete an entry within the loop. But it is not used to protect against a 
deletion from another core.
Did I misunderstand the logic? If not, we possibly want to use a 
readlock (over the existing spinlock).
Cheers,

--
Julien Grall