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From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: iommu@lists.linux-foundation.org,
	LKML <linux-kernel@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	Raj Ashok <ashok.raj@intel.com>,
	Jean Delvare <khali@linux-fr.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Lu Baolu" <baolu.lu@linux.intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: [PATCH v5 15/23] iommu: handle page response timeout
Date: Fri, 11 May 2018 13:54:07 -0700	[thread overview]
Message-ID: <1526072055-86990-16-git-send-email-jacob.jun.pan@linux.intel.com> (raw)
In-Reply-To: <1526072055-86990-1-git-send-email-jacob.jun.pan@linux.intel.com>

When IO page faults are reported outside IOMMU subsystem, the page
request handler may fail for various reasons. E.g. a guest received
page requests but did not have a chance to run for a long time. The
irresponsive behavior could hold off limited resources on the pending
device.
There can be hardware or credit based software solutions as suggested
in the PCI ATS Ch-4. To provide a basic safty net this patch
introduces a per device deferrable timer which monitors the longest
pending page fault that requires a response. Proper action such as
sending failure response code could be taken when timer expires but not
included in this patch. We need to consider the life cycle of page
groupd ID to prevent confusion with reused group ID by a device.
For now, a warning message provides clue of such failure.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
---
 drivers/iommu/iommu.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/iommu.h |  4 ++++
 2 files changed, 57 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 02fed3e..1f2f49e 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -827,6 +827,37 @@ int iommu_group_unregister_notifier(struct iommu_group *group,
 }
 EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
 
+static void iommu_dev_fault_timer_fn(struct timer_list *t)
+{
+	struct iommu_fault_param *fparam = from_timer(fparam, t, timer);
+	struct iommu_fault_event *evt;
+
+	u64 now;
+
+	now = get_jiffies_64();
+
+	/* The goal is to ensure driver or guest page fault handler(via vfio)
+	 * send page response on time. Otherwise, limited queue resources
+	 * may be occupied by some irresponsive guests or drivers.
+	 * When per device pending fault list is not empty, we periodically checks
+	 * if any anticipated page response time has expired.
+	 *
+	 * TODO:
+	 * We could do the following if response time expires:
+	 * 1. send page response code FAILURE to all pending PRQ
+	 * 2. inform device driver or vfio
+	 * 3. drain in-flight page requests and responses for this device
+	 * 4. clear pending fault list such that driver can unregister fault
+	 *    handler(otherwise blocked when pending faults are present).
+	 */
+	list_for_each_entry(evt, &fparam->faults, list) {
+		if (time_after64(now, evt->expire))
+			pr_err("Page response time expired!, pasid %d gid %d exp %llu now %llu\n",
+				evt->pasid, evt->page_req_group_id, evt->expire, now);
+	}
+	mod_timer(t, now + prq_timeout);
+}
+
 /**
  * iommu_register_device_fault_handler() - Register a device fault handler
  * @dev: the device
@@ -879,6 +910,9 @@ int iommu_register_device_fault_handler(struct device *dev,
 	param->fault_param->data = data;
 	INIT_LIST_HEAD(&param->fault_param->faults);
 
+	if (prq_timeout)
+		timer_setup(&param->fault_param->timer, iommu_dev_fault_timer_fn,
+			TIMER_DEFERRABLE);
 done_unlock:
 	mutex_unlock(&param->lock);
 
@@ -935,6 +969,8 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
 {
 	int ret = 0;
 	struct iommu_fault_event *evt_pending;
+	struct timer_list *tmr;
+	u64 exp;
 	struct iommu_fault_param *fparam;
 
 	/* iommu_param is allocated when device is added to group */
@@ -955,7 +991,17 @@ int iommu_report_device_fault(struct device *dev, struct iommu_fault_event *evt)
 			ret = -ENOMEM;
 			goto done_unlock;
 		}
+		/* Keep track of response expiration time */
+		exp = get_jiffies_64() + prq_timeout;
+		evt_pending->expire = exp;
 		mutex_lock(&fparam->lock);
+		if (list_empty(&fparam->faults)) {
+			/* First pending event, start timer */
+			tmr = &dev->iommu_param->fault_param->timer;
+			WARN_ON(timer_pending(tmr));
+			mod_timer(tmr, exp);
+		}
+
 		list_add_tail(&evt_pending->list, &fparam->faults);
 		mutex_unlock(&fparam->lock);
 	}
@@ -1572,6 +1618,13 @@ int iommu_page_response(struct device *dev,
 		}
 	}
 
+	/* stop response timer if no more pending request */
+	if (list_empty(&param->fault_param->faults) &&
+		timer_pending(&param->fault_param->timer)) {
+		pr_debug("no pending PRQ, stop timer\n");
+		del_timer(&param->fault_param->timer);
+	}
+
 done_unlock:
 	mutex_unlock(&param->fault_param->lock);
 	return ret;
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 722b90f..f3665b7 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -360,6 +360,7 @@ enum iommu_fault_reason {
  * @iommu_private: used by the IOMMU driver for storing fault-specific
  *                 data. Users should not modify this field before
  *                 sending the fault response.
+ * @expire: time limit in jiffies will wait for page response
  */
 struct iommu_fault_event {
 	struct list_head list;
@@ -373,6 +374,7 @@ struct iommu_fault_event {
 	u32 prot;
 	u64 device_private;
 	u64 iommu_private;
+	u64 expire;
 };
 
 /**
@@ -380,11 +382,13 @@ struct iommu_fault_event {
  * @dev_fault_handler: Callback function to handle IOMMU faults at device level
  * @data: handler private data
  * @faults: holds the pending faults which needs response, e.g. page response.
+ * @timer: track page request pending time limit
  * @lock: protect pending PRQ event list
  */
 struct iommu_fault_param {
 	iommu_dev_fault_handler_t handler;
 	struct list_head faults;
+	struct timer_list timer;
 	struct mutex lock;
 	void *data;
 };
-- 
2.7.4

  parent reply	other threads:[~2018-05-11 20:54 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-11 20:53 [PATCH v5 00/23] IOMMU and VT-d driver support for Shared Virtual Address (SVA) Jacob Pan
2018-05-11 20:53 ` [PATCH v5 01/23] iommu: introduce bind_pasid_table API function Jacob Pan
2018-08-23 16:34   ` Auger Eric
2018-08-24 12:47     ` Liu, Yi L
2018-08-24 13:20       ` Auger Eric
2018-08-28 17:04         ` Jacob Pan
2018-08-24 15:00   ` Auger Eric
2018-08-28  5:14     ` Jacob Pan
2018-08-28  8:34       ` Auger Eric
2018-08-28 16:36         ` Jacob Pan
2018-05-11 20:53 ` [PATCH v5 02/23] iommu/vt-d: move device_domain_info to header Jacob Pan
2018-05-11 20:53 ` [PATCH v5 03/23] iommu/vt-d: add a flag for pasid table bound status Jacob Pan
2018-05-13  7:33   ` Lu Baolu
2018-05-14 18:51     ` Jacob Pan
2018-05-13  8:01   ` Lu Baolu
2018-05-14 18:52     ` Jacob Pan
2018-05-11 20:53 ` [PATCH v5 04/23] iommu/vt-d: add bind_pasid_table function Jacob Pan
2018-05-13  9:29   ` Lu Baolu
2018-05-14 20:22     ` Jacob Pan
2018-05-11 20:53 ` [PATCH v5 05/23] iommu: introduce iommu invalidate API function Jacob Pan
2018-05-11 20:53 ` [PATCH v5 06/23] iommu/vt-d: add definitions for PFSID Jacob Pan
2018-05-14  1:36   ` Lu Baolu
2018-05-14 20:30     ` Jacob Pan
2018-05-11 20:53 ` [PATCH v5 07/23] iommu/vt-d: fix dev iotlb pfsid use Jacob Pan
2018-05-14  1:52   ` Lu Baolu
2018-05-14 20:38     ` Jacob Pan
2018-05-11 20:54 ` [PATCH v5 08/23] iommu/vt-d: support flushing more translation cache types Jacob Pan
2018-05-14  2:18   ` Lu Baolu
2018-05-14 20:46     ` Jacob Pan
2018-05-17  8:44   ` kbuild test robot
2018-05-11 20:54 ` [PATCH v5 09/23] iommu/vt-d: add svm/sva invalidate function Jacob Pan
2018-05-14  3:35   ` Lu Baolu
2018-05-14 20:49     ` Jacob Pan
2018-05-11 20:54 ` [PATCH v5 10/23] iommu: introduce device fault data Jacob Pan
2018-09-21 10:07   ` Auger Eric
2018-09-21 17:05     ` Jacob Pan
2018-09-26 10:20       ` Auger Eric
2018-05-11 20:54 ` [PATCH v5 11/23] driver core: add per device iommu param Jacob Pan
2018-05-14  5:27   ` Lu Baolu
2018-05-14 20:52     ` Jacob Pan
2018-05-11 20:54 ` [PATCH v5 12/23] iommu: add a timeout parameter for prq response Jacob Pan
2018-05-11 20:54 ` [PATCH v5 13/23] iommu: introduce device fault report API Jacob Pan
2018-05-14  6:01   ` Lu Baolu
2018-05-14 20:55     ` Jacob Pan
2018-05-15  6:52       ` Lu Baolu
2018-05-17 11:41   ` Liu, Yi L
2018-05-17 15:59     ` Jacob Pan
2018-05-17 23:22       ` Liu, Yi L
2018-05-21 23:03         ` Jacob Pan
2018-09-06  9:25   ` Auger Eric
2018-09-06 12:42     ` Jean-Philippe Brucker
2018-09-06 13:14       ` Auger Eric
2018-09-06 17:06         ` Jean-Philippe Brucker
2018-09-07  7:11           ` Auger Eric
2018-09-07 11:23             ` Jean-Philippe Brucker
2018-09-14 13:24   ` Auger Eric
2018-09-17 16:57     ` Jacob Pan
2018-09-25 14:58   ` Jean-Philippe Brucker
2018-09-25 22:17     ` Jacob Pan
2018-09-26 10:14       ` Jean-Philippe Brucker
2018-05-11 20:54 ` [PATCH v5 14/23] iommu: introduce page response function Jacob Pan
2018-05-14  6:39   ` Lu Baolu
2018-05-29 16:13     ` Jacob Pan
2018-09-10 14:52   ` Auger Eric
2018-09-10 17:50     ` Jacob Pan
2018-09-10 19:06       ` Auger Eric
2018-05-11 20:54 ` Jacob Pan [this message]
2018-05-14  7:43   ` [PATCH v5 15/23] iommu: handle page response timeout Lu Baolu
2018-05-29 16:20     ` Jacob Pan
2018-05-30  7:46       ` Lu Baolu
2018-05-11 20:54 ` [PATCH v5 16/23] iommu/config: add build dependency for dmar Jacob Pan
2018-05-11 20:54 ` [PATCH v5 17/23] iommu/vt-d: report non-recoverable faults to device Jacob Pan
2018-05-14  8:17   ` Lu Baolu
2018-05-29 17:33     ` Jacob Pan
2018-05-11 20:54 ` [PATCH v5 18/23] iommu/intel-svm: report device page request Jacob Pan
2018-05-11 20:54 ` [PATCH v5 19/23] iommu/intel-svm: replace dev ops with fault report API Jacob Pan
2018-05-11 20:54 ` [PATCH v5 20/23] iommu/intel-svm: do not flush iotlb for viommu Jacob Pan
2018-05-11 20:54 ` [PATCH v5 21/23] iommu/vt-d: add intel iommu page response function Jacob Pan
2018-05-11 20:54 ` [PATCH v5 22/23] trace/iommu: add sva trace events Jacob Pan
2018-05-11 20:54 ` [PATCH v5 23/23] iommu: use sva invalidate and device fault trace event Jacob Pan
2018-05-29 15:54 ` [PATCH v5 00/23] IOMMU and VT-d driver support for Shared Virtual Address (SVA) Jacob Pan

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