From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: 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>,
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>,
jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH v5 15/23] iommu: handle page response timeout
Date: Tue, 29 May 2018 09:20:58 -0700 [thread overview]
Message-ID: <20180529092058.1942b223@jacob-builder> (raw)
In-Reply-To: <5AF93E3A.2040902@linux.intel.com>
On Mon, 14 May 2018 15:43:54 +0800
Lu Baolu <baolu.lu@linux.intel.com> wrote:
> Hi,
>
> On 05/12/2018 04:54 AM, Jacob Pan wrote:
> > 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);
> > +}
> > +
>
> This timer scheme is very rough.
>
yes, the timer is a rough safety net for misbehaved PRQ handlers such
as a guest.
> The timer expires every 10 seconds (by default).
>
> 0 10 20
> 30 40
> +---------------+---------------+---------------+---------------+ ^
> ^ ^ ^ ^ | | |
> | | F0 F1 F2 F3
> (F1,F2,F3 will not be handled until here!)
>
> F0, F1, F2, F3 are four page faults happens during [0, 10s) time
> window. F1, F2, F3 timeout won't be handled until the timer expires
> again at 20s. That means a fault might be pending there until about
> (2 * prq_timeout) seconds later.
>
correct. it could be 2x for the worst case. I should explain in
comments.
> Out of curiosity, Why not adding a timer in iommu_fault_event,
> starting it in iommu_report_device_fault() and removing it in
> iommu_page_response()?
>
I thought about that also but since we are just trying to have a broad
and rough safety net (in addition to potential HW mechanism or credit
based solution), my thought was that having a per device timer is more
economical than per event.
Thanks for the in-depth check!
> Best regards,
> Lu Baolu
>
>
> [...]
>
[Jacob Pan]
next prev parent reply other threads:[~2018-05-29 16:18 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 ` [PATCH v5 15/23] iommu: handle page response timeout Jacob Pan
2018-05-14 7:43 ` Lu Baolu
2018-05-29 16:20 ` Jacob Pan [this message]
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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