Linux-ACPI Archive on lore.kernel.org
 help / color / Atom feed
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: joro@8bytes.org, will@kernel.org
Cc: lorenzo.pieralisi@arm.com, robh+dt@kernel.org,
	guohanjun@huawei.com, sudeep.holla@arm.com, rjw@rjwysocki.net,
	lenb@kernel.org, robin.murphy@arm.com,
	Jonathan.Cameron@huawei.com, eric.auger@redhat.com,
	iommu@lists.linux-foundation.org, devicetree@vger.kernel.org,
	linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-accelerators@lists.ozlabs.org, baolu.lu@linux.intel.com,
	jacob.jun.pan@linux.intel.com, kevin.tian@intel.com,
	vdumpa@nvidia.com, zhangfei.gao@linaro.org,
	shameerali.kolothum.thodi@huawei.com, vivek.gautam@arm.com,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Rob Herring <robh@kernel.org>
Subject: [PATCH v11 08/10] dt-bindings: document stall property for IOMMU masters
Date: Mon, 25 Jan 2021 12:06:49 +0100
Message-ID: <20210125110650.3232195-9-jean-philippe@linaro.org> (raw)
In-Reply-To: <20210125110650.3232195-1-jean-philippe@linaro.org>

On ARM systems, some platform devices behind an IOMMU may support stall,
which is the ability to recover from page faults. Let the firmware tell us
when a device supports stall.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 .../devicetree/bindings/iommu/iommu.txt        | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt b/Documentation/devicetree/bindings/iommu/iommu.txt
index 3c36334e4f94..26ba9e530f13 100644
--- a/Documentation/devicetree/bindings/iommu/iommu.txt
+++ b/Documentation/devicetree/bindings/iommu/iommu.txt
@@ -92,6 +92,24 @@ Optional properties:
   tagging DMA transactions with an address space identifier. By default,
   this is 0, which means that the device only has one address space.
 
+- dma-can-stall: When present, the master can wait for a transaction to
+  complete for an indefinite amount of time. Upon translation fault some
+  IOMMUs, instead of aborting the translation immediately, may first
+  notify the driver and keep the transaction in flight. This allows the OS
+  to inspect the fault and, for example, make physical pages resident
+  before updating the mappings and completing the transaction. Such IOMMU
+  accepts a limited number of simultaneous stalled transactions before
+  having to either put back-pressure on the master, or abort new faulting
+  transactions.
+
+  Firmware has to opt-in stalling, because most buses and masters don't
+  support it. In particular it isn't compatible with PCI, where
+  transactions have to complete before a time limit. More generally it
+  won't work in systems and masters that haven't been designed for
+  stalling. For example the OS, in order to handle a stalled transaction,
+  may attempt to retrieve pages from secondary storage in a stalled
+  domain, leading to a deadlock.
+
 
 Notes:
 ======
-- 
2.30.0


  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-25 11:06 [PATCH v11 00/10] iommu: I/O page faults for SMMUv3 Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 01/10] iommu: Fix comment for struct iommu_fwspec Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 02/10] iommu/arm-smmu-v3: Use device properties for pasid-num-bits Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 03/10] iommu: Separate IOMMU_DEV_FEAT_IOPF from IOMMU_DEV_FEAT_SVA Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 04/10] iommu/vt-d: Support IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 05/10] uacce: Enable IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 06/10] iommu: Add a page fault handler Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 07/10] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2021-01-25 11:06 ` Jean-Philippe Brucker [this message]
2021-01-25 11:06 ` [PATCH v11 09/10] ACPI/IORT: Enable stall support for platform devices Jean-Philippe Brucker
2021-01-25 11:06 ` [PATCH v11 10/10] iommu/arm-smmu-v3: Add " Jean-Philippe Brucker
2021-01-25 13:50   ` Jonathan Cameron
2021-01-25 15:46     ` Jean-Philippe Brucker

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=20210125110650.3232195-9-jean-philippe@linaro.org \
    --to=jean-philippe@linaro.org \
    --cc=Jonathan.Cameron@huawei.com \
    --cc=baolu.lu@linux.intel.com \
    --cc=devicetree@vger.kernel.org \
    --cc=eric.auger@redhat.com \
    --cc=guohanjun@huawei.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.jun.pan@linux.intel.com \
    --cc=joro@8bytes.org \
    --cc=kevin.tian@intel.com \
    --cc=lenb@kernel.org \
    --cc=linux-accelerators@lists.ozlabs.org \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=lorenzo.pieralisi@arm.com \
    --cc=rjw@rjwysocki.net \
    --cc=robh+dt@kernel.org \
    --cc=robh@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=shameerali.kolothum.thodi@huawei.com \
    --cc=sudeep.holla@arm.com \
    --cc=vdumpa@nvidia.com \
    --cc=vivek.gautam@arm.com \
    --cc=will@kernel.org \
    --cc=zhangfei.gao@linaro.org \
    /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

Linux-ACPI Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-acpi/0 linux-acpi/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-acpi linux-acpi/ https://lore.kernel.org/linux-acpi \
		linux-acpi@vger.kernel.org
	public-inbox-index linux-acpi

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-acpi


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git