LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Auger Eric <eric.auger@redhat.com>
To: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>,
	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>
Cc: Jean Delvare <khali@linux-fr.org>,
	Rafael Wysocki <rafael.j.wysocki@intel.com>,
	Raj Ashok <ashok.raj@intel.com>
Subject: Re: [PATCH v5 13/23] iommu: introduce device fault report API
Date: Fri, 7 Sep 2018 09:11:14 +0200	[thread overview]
Message-ID: <953746f3-352b-cd17-9938-eb78af3b58a9@redhat.com> (raw)
In-Reply-To: <289610e3-2633-e448-259c-194e6f2c2b52@arm.com>

Hi Jean-Philippe,

On 09/06/2018 07:06 PM, Jean-Philippe Brucker wrote:
> On 06/09/2018 14:14, Auger Eric wrote:
>> Hi Jean-Philippe,
>>
>> On 09/06/2018 02:42 PM, Jean-Philippe Brucker wrote:
>>> On 06/09/2018 10:25, Auger Eric wrote:
>>>>> +		mutex_lock(&fparam->lock);
>>>>> +		list_add_tail(&evt_pending->list, &fparam->faults);
>>>> same doubt as Yi Liu. You cannot rely on the userspace willingness to
>>>> void the queue and deallocate this memory.
>>
>> By the way I saw there is a kind of garbage collectors for faults which
>> wouldn't have received any responses. However I am not sure this removes
>> the concern of having the fault list on kernel side growing beyond
>> acceptable limits.
> 
> How about per-device quotas? (https://lkml.org/lkml/2018/4/23/706 for
> reference) With PRI the IOMMU driver already sets per-device credits
> when initializing the device (pci_enable_pri), so if the device behaves
> properly it shouldn't send new page requests once the number of
> outstanding ones is maxed out.

But this needs to work for non PRI use case too?
> 
> The stall mode of SMMU doesn't have per-device limit, and depending on
> the implementation it might be easy for one guest using stall to prevent
> other guests from receiving faults. For this reason we'll have to
> enforce a per-device stall quota in the SMMU driver, and immediately
> terminate faults that exceed this quota. We could easily do the same for
> PRI, if we don't trust devices to follow the spec. The difficult part is
> finding the right number of credits...
> 
>>> Host device drivers that use this API to be notified on fault can't deal
>>> with arch-specific event formats (SMMU event, Vt-d fault event, etc), so
>>> the APIs should be arch-agnostic. Given that requirement, using a single
>>> iommu_fault_event structure for both PRI and event queues made sense,
>>> especially since the even queue can have stall events that look a lot
>>> like PRI page requests.
>> I understand the data structure needs to be generic. Now I guess PRI
>> events and other standard translator error events (that can happen
>> without PRI) may have different characteristics in event fields,
> 
> Right, an event contains more information than a PRI page request.
> Stage-2 fields (CLASS, S2, IPA, TTRnW) cannot be represented by
> iommu_fault_event at the moment.

Yes I am currently doing the mapping exercise between SMMUv3 events and
iommu_fault_event and I miss config errors for instance.
 For precise emulation it might be
> useful to at least add the S2 flag (as a new iommu_fault_reason?), so
> that when the guest maps stage-1 to an invalid GPA, QEMU could for
> example inject an external abort.

Actually we may even need to filter events and return to the guest only
the S1 related.
> 
>> queue
>> size, that may deserve to create different APIs and internal data
>> structs. Also this may help separating the concerns.
> 
> It might duplicate them. If the consumer of the event report is a host
> device driver, the SMMU needs to report a "generic" iommu_fault_event,
> and if the consumer is VFIO it would report a specialized one

I am unsure of my understanding of the UNRECOVERABLE error type. Is it
everything else than a PRI. For instance are all SMMUv3 event errors
supposed to be put under the IOMMU_FAULT_DMA_UNRECOV umbrella?

If I understand correctly there are different consumers for PRI and
unrecoverable data, so why not having 2 different APIs.
> 
>> My remark also
>> stems from the fact the SMMU uses 2 different queues, whose size can
>> also be different.
> 
> Hm, for PRI requests the kernel-userspace queue size should actually be
> the number of PRI credits for that device. Hadn't thought about it
> before, where do we pass that info to userspace?
Cannot help here at the moment, sorry.
 For fault events, the
> queue could be as big as the SMMU event queue, though using all that
> space might be wasteful.
The guest has its own programming of the SMMU_EVENTQ_BASE.LOG2SIZE. This
could be used to program the SW fifo

 Non-stalled events should be rare and reporting
> them isn't urgent. Stalled ones would need the number of stall credits I
> mentioned above, which realistically will be a lot less than the SMMU
> event queue size. Given that a device will use either PRI or stall but
> not both, I still think events and PRI could go through the same queue.
Did I get it right PRI is for PCIe and STALL for non PCIe? But all that
stuff also is related to Page Request use case, right?

Thanks

Eric
> 
> Thanks,
> Jean
> 

  reply	other threads:[~2018-09-07  7:11 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 [this message]
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
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=953746f3-352b-cd17-9938-eb78af3b58a9@redhat.com \
    --to=eric.auger@redhat.com \
    --cc=alex.williamson@redhat.com \
    --cc=ashok.raj@intel.com \
    --cc=dwmw2@infradead.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.jun.pan@linux.intel.com \
    --cc=jean-philippe.brucker@arm.com \
    --cc=joro@8bytes.org \
    --cc=khali@linux-fr.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=rafael.j.wysocki@intel.com \
    --subject='Re: [PATCH v5 13/23] iommu: introduce device fault report API' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).