From nobody Wed Oct 8 16:04:24 2025 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 10D7F2EF2A6; Thu, 26 Jun 2025 18:45:37 +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=1750963539; cv=none; b=IXPIsuCZDeq6VimRvD5IUw9VRNoSQmd/iSF2j2eXrinjrkto+y54iXVIBFZFCjvAXIBXT990YAXbE02aF9aSyxyv124IC/GQISDgMDV2z/TgZ6h6ffdCJeC5APvvApQTOazNwCHhzj2fcCNesiFgvskfaCcj1DTyEarBWyECDCk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750963539; c=relaxed/simple; bh=LZaIsLivWrm8jAuNh46A+s8OExisEIxeFrTonwFIkBY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BVxEujur/iDDjt8kJK6hn9Hv/JecDwPcaygwr32s/sn12YK9CMkHAubLrNa2ELgj6Nvqr7TZC6pmiHXt5ure6bKczIkPhUdJoEfomHgMr/j5KHvrHz4LsdXmhaeaXQ8xXDWQM+CfGrjPhG6PoINrrLNz7ZqnlEG5GA7JgPOTbwE= 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 B2093271B; Thu, 26 Jun 2025 11:45:19 -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 2686A3F66E; Thu, 26 Jun 2025 11:45:37 -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 v8 3/3] tpm_crb_ffa: handle tpm busy return code Date: Thu, 26 Jun 2025 13:45:21 -0500 Message-ID: <20250626184521.1079507-4-prachotan.bathi@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250626184521.1079507-1-prachotan.bathi@arm.com> References: <20250626184521.1079507-1-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 --- .../admin-guide/kernel-parameters.txt | 8 +++ drivers/char/tpm/tpm_crb_ffa.c | 49 ++++++++++++++++--- 2 files changed, 50 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index f1f2c0874da9..eb1ebbc328ab 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 397cc3b0a478..a6c9e9c2c344 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 =20 #include +#include +#include #include "tpm_crb_ffa.h" =20 #define memzero(s, n) memset((s), 0, (n)) @@ -180,17 +182,13 @@ 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)) { @@ -221,6 +219,43 @@ 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 unsigned int busy_timeout_ms =3D 2000; +/** + * This parameter defines the maximum time in milliseconds to retry + * sending a message to the TPM service before giving up. + */ +module_param(busy_timeout_ms, uint, 0644); +MODULE_PARM_DESC(busy_timeout_ms, + "Maximum time in ms to retry before giving up on busy"); + +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