Re: [PATCH] arm: optee: don't print warning about "wrong" RPC buffer

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 5 Oct 2020, Volodymyr Babchuk wrote:
> OP-TEE mediator tracks cookie value for a last buffer which
> was requested by OP-TEE. This tracked value serves one important
> purpose: if OP-TEE wants to request another buffer, we know
> that it finished importing previous one and we can free page list
> associated with it.
> 
> Also, we had false premise that OP_TEE will free requested buffers in
> reversed order. So we checked rpc_data_cookie during handling
> OPTEE_RPC_CMD_SHM_FREE call and printed warning if cookie of buffer
> which is requested to be freed differs from last allocated one.
> 
> During testing RPMB FS services I discovered, that RPMB code frees
> request and response buffers in the same order is it allocated
> them. And this is perfectly fine, actually.
> 
> So, we are removing mentioned warning message in Xen, as it is
> perfectly normal to free buffers in arbitrary order.
> 
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>


Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

I am going to fix the grammar on commit


> ---
>  xen/arch/arm/tee/optee.c | 20 +-------------------
>  1 file changed, 1 insertion(+), 19 deletions(-)
> 
> diff --git a/xen/arch/arm/tee/optee.c b/xen/arch/arm/tee/optee.c
> index 8a39fe33b0..ee85359742 100644
> --- a/xen/arch/arm/tee/optee.c
> +++ b/xen/arch/arm/tee/optee.c
> @@ -1127,25 +1127,7 @@ static int handle_rpc_return(struct optee_domain *ctx,
>           */
>          if ( shm_rpc->xen_arg->cmd == OPTEE_RPC_CMD_SHM_FREE )
>          {
> -            uint64_t cookie = shm_rpc->xen_arg->params[0].u.value.b;
> -
> -            free_optee_shm_buf(ctx, cookie);
> -
> -            /*
> -             * OP-TEE asks to free the buffer, but this is not the same
> -             * buffer we previously allocated for it. While nothing
> -             * prevents OP-TEE from asking this, it is the strange
> -             * situation. This may or may not be caused by a bug in
> -             * OP-TEE or mediator. But is better to print warning.
> -             */
> -            if ( call->rpc_data_cookie && call->rpc_data_cookie != cookie )
> -            {
> -                gprintk(XENLOG_ERR,
> -                        "Saved RPC cookie does not corresponds to OP-TEE's 
> (%"PRIx64" != %"PRIx64")\n",
> -                        call->rpc_data_cookie, cookie);
> -
> -                WARN();
> -            }
> +            free_optee_shm_buf(ctx, shm_rpc->xen_arg->params[0].u.value.b);
>              call->rpc_data_cookie = 0;
>          }
>          unmap_domain_page(shm_rpc->xen_arg);
> -- 
> 2.27.0
>