From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 19ABE2EF650; Tue, 17 Jun 2025 14:40:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750171229; cv=none; b=GaUkQhvXDZuqw5bAGTNeL0U5MY3ZnewDL7LwKq4aLF77NsplGbV6hh+3Snlf2FrZkelStojUdmNhSWz/2eAswxswKgGfjWsO+lw75LtfdP8K3s6UFCn6ZvySXRFeb7fNANUJST9G8XIhCn9UBIOqIx0bdIbx5dEu5Veyvyq4sB8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750171229; c=relaxed/simple; bh=1sJ5uWIyOK0PQu9DY5SEJMP6Y603O+MTzVrgiX+WWWE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Eqh3V5ibS8EKUPgLgwPdIZ/D7/+nAvuKG4uE5TT5ynhYAgSwmaMPKYY+qImTYc+7re/H7+XBuNhGGzIF2cZdRjNoahmkR1XauM5nx94N/9E0z8tC8VhB1PRHuvjeje2QHAzC+VxVVDns0mx+RSodVexrdbIPdq7i4Zw8Ex7Q0nY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Dd/OpOql; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dd/OpOql" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 59DECC4CEE3; Tue, 17 Jun 2025 14:40:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750171228; bh=1sJ5uWIyOK0PQu9DY5SEJMP6Y603O+MTzVrgiX+WWWE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Dd/OpOqle3v9pBIn0wbR/lhVL7fG5NubWL79DTXE8GaZhu7yETpIVDN1UDnzdPoTt u53t5A2GG4VvYecoFkbiXWQuwi28VVIhuN22J/CPVAcG+dVfwUcaHC64fxXIqEcf6M mGV0pioxsB1tDCqt085N5f2Q5Q+85XjfZlpFQu0o11snNphd/ml/2FxFOxUqIv5BBw yt+8jrLV/JfgOchJA/DNn6WY+V/ARiVCUDS+Kdz41HVOZ8Zkj0DTb0ouvA35I3H4uz CCqoQe7TThtnBq3KGhg23lJz1aEmnd0iJglNJxBcHkqI82kEpEl3aRmCNvPHM3fgv5 rJ3Cb6E5uaXoA== Date: Tue, 17 Jun 2025 17:40:24 +0300 From: Jarkko Sakkinen To: Prachotan Bathi Cc: Peter Huewe , Jason Gunthorpe , Stuart Yoder , linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/1] tpm_crb_ffa: handle tpm busy return code Message-ID: References: <20250613233132.4167653-1-prachotan.bathi@arm.com> <20250613233132.4167653-2-prachotan.bathi@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250613233132.4167653-2-prachotan.bathi@arm.com> On Fri, Jun 13, 2025 at 06:31:32PM -0500, Prachotan Bathi wrote: > For CRB over FF-A interface, if the firmwre TPM or TPM service [1] shares > its Secure Partition (SP) with another service, message requests may > fail with a -EBUSY error. Platforms supporting direct message request v2[1] > can support secure partitions that support multiple services. > > To handle this, replace the single check and call with a retry loop > that attempts the TPM message send operation until it succeeds or a > configurable timeout is reached. The retry mechanism introduces a > module parameter (`busy_timeout`, default: 2000ms) to control how long > to keep retrying on -EBUSY responses. Between retries, the code waits > briefly (50-100 microseconds) to avoid busy-waiting and handling > TPM BUSY conditions more gracefully. > > [1] TPM Service Command Response Buffer Interface Over FF-A > https://developer.arm.com/documentation/den0138/latest/ > > Signed-off-by: Prachotan Bathi > --- > drivers/char/tpm/tpm_crb_ffa.c | 74 +++++++++++++++++++++++----------- > 1 file changed, 50 insertions(+), 24 deletions(-) > > diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c > index 4ead61f01299..e47e110bac9e 100644 > --- a/drivers/char/tpm/tpm_crb_ffa.c > +++ b/drivers/char/tpm/tpm_crb_ffa.c > @@ -10,6 +10,8 @@ > #define pr_fmt(fmt) "CRB_FFA: " fmt > > #include > +#include > +#include > #include "tpm_crb_ffa.h" > > /* TPM service function status codes */ > @@ -178,6 +180,17 @@ int tpm_crb_ffa_init(void) > } > EXPORT_SYMBOL_GPL(tpm_crb_ffa_init); > > +static unsigned int busy_timeout = 2000; > +/** > + * busy_timeout - Maximum time to retry before giving up on busy > + * > + * This parameter defines the maximum time in milliseconds to retry > + * sending a message to the TPM service before giving up. > + */ > +module_param(busy_timeout, uint, 0644); > +MODULE_PARM_DESC(busy_timeout, > + "Maximum time to retry before giving up on busy"); > + > static int __tpm_crb_ffa_send_recieve(unsigned long func_id, there's BTW a typo ;-) s/recieve/receive Not your fault but maybe it would make sense to correct that anyhow... > unsigned long a0, > unsigned long a1, > @@ -191,34 +204,47 @@ static int __tpm_crb_ffa_send_recieve(unsigned long func_id, Maybe this would be less exhausting if you instead would work out the existing function something like __tpm_crb_ffa_try_send_receive() and call that in a loop? It would be then similar organization as with tpm_transmit(). > > msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops; > > - if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) { > - memset(&tpm_crb_ffa->direct_msg_data2, 0x00, > - sizeof(struct ffa_send_direct_data2)); > + ktime_t start; > + ktime_t stop; > + > + start = ktime_get(); > + stop = ktime_add(start, ms_to_ktime(busy_timeout)); > + > + do { > + if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) { > + memset(&tpm_crb_ffa->direct_msg_data2, 0x00, > + sizeof(struct ffa_send_direct_data2)); nit: could use memzero() instead. > > - tpm_crb_ffa->direct_msg_data2.data[0] = func_id; > - tpm_crb_ffa->direct_msg_data2.data[1] = a0; > - tpm_crb_ffa->direct_msg_data2.data[2] = a1; > - tpm_crb_ffa->direct_msg_data2.data[3] = a2; > + tpm_crb_ffa->direct_msg_data2.data[0] = func_id; > + tpm_crb_ffa->direct_msg_data2.data[1] = a0; > + tpm_crb_ffa->direct_msg_data2.data[2] = a1; > + tpm_crb_ffa->direct_msg_data2.data[3] = a2; > > - ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev, > + ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev, > &tpm_crb_ffa->direct_msg_data2); > - if (!ret) > - ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]); > - } else { > - memset(&tpm_crb_ffa->direct_msg_data, 0x00, > - sizeof(struct ffa_send_direct_data)); > - > - tpm_crb_ffa->direct_msg_data.data1 = func_id; > - tpm_crb_ffa->direct_msg_data.data2 = a0; > - tpm_crb_ffa->direct_msg_data.data3 = a1; > - tpm_crb_ffa->direct_msg_data.data4 = a2; > - > - ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev, > - &tpm_crb_ffa->direct_msg_data); > - if (!ret) > - ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1); > - } > + if (!ret) > + ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]); > + } else { > + memset(&tpm_crb_ffa->direct_msg_data, 0x00, > + sizeof(struct ffa_send_direct_data)); > > + tpm_crb_ffa->direct_msg_data.data1 = func_id; > + tpm_crb_ffa->direct_msg_data.data2 = a0; > + tpm_crb_ffa->direct_msg_data.data3 = a1; > + tpm_crb_ffa->direct_msg_data.data4 = a2; > + > + ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev, > + &tpm_crb_ffa->direct_msg_data); > + if (!ret) > + ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1); > + } > + if (ret == -EBUSY) > + pr_err("TPM says busy, trying again, value, ret: %d\n", > + ret); This is not an error condition but instead a legit condition, as far as kernel is considered. Please, remove pr_err(). > + else > + break; > + usleep_range(50, 100); > + } while (ktime_before(ktime_get(), stop)); > > return ret; > } > -- > 2.43.0 > BR, Jarkko