From nobody Tue Oct 7 16:40:40 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 592702367BF; Tue, 8 Jul 2025 22:52:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752015150; cv=none; b=l7NH3e0TFlS5ZNuFEVzz5HeMaqXOV9PeGSLN9/IJSEarHu95Ls2tifx02q//hDM1Pr2+M82tmiu0n4vO1GJLZWtmNqWLys7/2UMHYnbKlclo72RpmcGRIm8myc814L7Lol1FX7zLX2YtZikH9W63nWIOkJskKlqqd2D/VT5S8UA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752015150; c=relaxed/simple; bh=yfifoK1lCQIBGtO4PIoaGuKMpw1ve2V3EflpM9EmCY0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FX9LRQvZMrdOcmzAn7eAwFePxK2djuvs2W+k0O39P/kljOhsUwF9S7DjW6oUMugqayVZkH8gCNelzb+NbuzJCWBTO8lzsFQatm/vY/ZO3kwHJJ5CvtJ2CM2tW3N1+ucy/KAGzkTNdwyBZD8uuj8wpn4pIPo1cvjIIOaOx1iJq6M= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E4FA41764; Tue, 8 Jul 2025 15:52:15 -0700 (PDT) Received: from u103485.austin.arm.com (u103485.arm.com [10.118.30.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8F9EE3F66E; Tue, 8 Jul 2025 15:52:27 -0700 (PDT) From: Prachotan Bathi To: Peter Huewe , Jarkko Sakkinen , Jason Gunthorpe , Stuart Yoder Cc: linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, Prachotan Bathi Subject: [PATCH v9 3/3] tpm_crb_ffa: handle tpm busy return code Date: Tue, 8 Jul 2025 17:51:51 -0500 Message-ID: <20250708225151.2473657-4-prachotan.bathi@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250708225151.2473657-1-prachotan.bathi@arm.com> References: <20250708225151.2473657-1-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-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Platforms supporting direct message request v2 [1] can support secure partitions that support multiple services. For CRB over FF-A interface, if the firmware TPM or TPM service [1] shares its Secure Partition (SP) with another service, message requests may fail with a -EBUSY error. 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. Implement a _try_send_receive function to do a single send/receive and modify the existing send_receive to add this retry loop. The retry mechanism introduces a module parameter (`busy_timeout_ms`, 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. The parameter can be modified at run-time as such: echo 3000 | tee /sys/module/tpm_crb_ffa/parameters/busy_timeout_ms This changes the timeout from the default 2000ms to 3000ms. [1] TPM Service Command Response Buffer Interface Over FF-A https://developer.arm.com/documentation/den0138/latest/ Signed-off-by: Prachotan Bathi suggested-by to 2/3? --- .../admin-guide/kernel-parameters.txt | 8 ++++ drivers/char/tpm/tpm_crb_ffa.c | 45 ++++++++++++++++--- 2 files changed, 46 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 07e22ba5bfe3..343377538fe9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -7214,6 +7214,14 @@ causing a major performance hit, and the space where machines are deployed is by other means guarded. =20 + tpm_crb_ffa.busy_timeout_ms=3D [ARM64,TPM] + Maximum time in milliseconds to retry sending a message + to the TPM service before giving up. This parameter controls + how long the system will continue retrying when the TPM + service is busy. + Format: + Default: 2000 (2 seconds) + tpm_suspend_pcr=3D[HW,TPM] Format: integer pcr id Specify that at suspend time, the tpm driver diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c index 7faed6f3bf66..06599c07b746 100644 --- a/drivers/char/tpm/tpm_crb_ffa.c +++ b/drivers/char/tpm/tpm_crb_ffa.c @@ -10,8 +10,16 @@ #define pr_fmt(fmt) "CRB_FFA: " fmt =20 #include +#include +#include #include "tpm_crb_ffa.h" =20 +static unsigned int busy_timeout_ms =3D 2000; + +module_param(busy_timeout_ms, uint, 0644); +MODULE_PARM_DESC(busy_timeout_ms, + "Maximum time in ms to retry before giving up on busy"); + /* TPM service function status codes */ #define CRB_FFA_OK 0x05000001 #define CRB_FFA_OK_RESULTS_RETURNED 0x05000002 @@ -178,17 +186,13 @@ int tpm_crb_ffa_init(void) } EXPORT_SYMBOL_GPL(tpm_crb_ffa_init); =20 -static int __tpm_crb_ffa_send_receive(unsigned long func_id, - unsigned long a0, - unsigned long a1, - unsigned long a2) +static int __tpm_crb_ffa_try_send_receive(unsigned long func_id, + unsigned long a0, unsigned long a1, + unsigned long a2) { const struct ffa_msg_ops *msg_ops; int ret; =20 - if (!tpm_crb_ffa) - return -ENOENT; - msg_ops =3D tpm_crb_ffa->ffa_dev->ops->msg_ops; =20 if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) { @@ -214,6 +218,33 @@ static int __tpm_crb_ffa_send_receive(unsigned long fu= nc_id, ret =3D tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1); } =20 + return ret; +} + +static int __tpm_crb_ffa_send_receive(unsigned long func_id, unsigned long= a0, + unsigned long a1, unsigned long a2) +{ + ktime_t start, stop; + int ret; + + if (!tpm_crb_ffa) + return -ENOENT; + + start =3D ktime_get(); + stop =3D ktime_add(start, ms_to_ktime(busy_timeout_ms)); + + for (;;) { + ret =3D __tpm_crb_ffa_try_send_receive(func_id, a0, a1, a2); + if (ret !=3D -EBUSY) + break; + + usleep_range(50, 100); + if (ktime_after(ktime_get(), stop)) { + dev_warn(&tpm_crb_ffa->ffa_dev->dev, + "Busy retry timed out\n"); + break; + } + } =20 return ret; } --=20 2.43.0