From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jacob Pan Subject: [PATCH v5 12/23] iommu: add a timeout parameter for prq response Date: Fri, 11 May 2018 13:54:04 -0700 Message-ID: <1526072055-86990-13-git-send-email-jacob.jun.pan@linux.intel.com> References: <1526072055-86990-1-git-send-email-jacob.jun.pan@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1526072055-86990-1-git-send-email-jacob.jun.pan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, LKML , Joerg Roedel , David Woodhouse , Greg Kroah-Hartman , Alex Williamson , Jean-Philippe Brucker Cc: Raj Ashok , Rafael Wysocki , Jean Delvare List-Id: iommu@lists.linux-foundation.org When an IO page request is processed outside IOMMU subsystem, response can be delayed or lost. Add a tunable setup parameter such that user can chooose the timeout for IOMMU to track pending page requests. This timeout mechanism is a basic safty net which can be implemented in conjunction with credit based or device level page response exception handling. Signed-off-by: Jacob Pan --- Documentation/admin-guide/kernel-parameters.txt | 8 +++++++ drivers/iommu/iommu.c | 28 +++++++++++++++++++++++++ 2 files changed, 36 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 11fc28e..5c1e836 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1718,6 +1718,14 @@ 1 - Bypass the IOMMU for DMA. unset - Use IOMMU translation for DMA. + iommu.prq_timeout= + Timeout in seconds to wait for page response + of a pending page request. + Format: + Default: 10 + 0 - no timeout tracking + 1 to 100 - allowed range + io7= [HW] IO7 for Marvel based alpha systems See comment before marvel_specify_io7 in arch/alpha/kernel/core_marvel.c. diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 784e019..3a49b96 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -37,6 +37,18 @@ static struct kset *iommu_group_kset; static DEFINE_IDA(iommu_group_ida); static unsigned int iommu_def_domain_type = IOMMU_DOMAIN_DMA; +/* + * Timeout to wait for page response of a pending page request. This is + * intended as a basic safty net in case a pending page request is not + * responded for an exceptionally long time. Device may also implement + * its own protection mechanism against this exception. + * Units are in jiffies with a range between 1 - 100 seconds equivalent. + * Default to 10 seconds. + * Setting 0 means no timeout tracking. + */ +#define IOMMU_PAGE_RESPONSE_MAX_TIMEOUT (HZ * 100) +#define IOMMU_PAGE_RESPONSE_DEF_TIMEOUT (HZ * 10) +static unsigned long prq_timeout = IOMMU_PAGE_RESPONSE_DEF_TIMEOUT; struct iommu_callback_data { const struct iommu_ops *ops; @@ -125,6 +137,22 @@ static int __init iommu_set_def_domain_type(char *str) } early_param("iommu.passthrough", iommu_set_def_domain_type); +static int __init iommu_set_prq_timeout(char *str) +{ + unsigned long timeout; + + if (!str) + return -EINVAL; + timeout = simple_strtoul(str, NULL, 0); + timeout = timeout * HZ; + if (timeout > IOMMU_PAGE_RESPONSE_MAX_TIMEOUT) + return -EINVAL; + prq_timeout = timeout; + + return 0; +} +early_param("iommu.prq_timeout", iommu_set_prq_timeout); + static ssize_t iommu_group_attr_show(struct kobject *kobj, struct attribute *__attr, char *buf) { -- 2.7.4