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 v10 08/10] dt-bindings: document stall property for IOMMU masters
Date: Thu, 21 Jan 2021 13:36:22 +0100 [thread overview]
Message-ID: <20210121123623.2060416-9-jean-philippe@linaro.org> (raw)
In-Reply-To: <20210121123623.2060416-1-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
next prev parent reply other threads:[~2021-01-21 12:42 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 12:36 [PATCH v10 00/10] iommu: I/O page faults for SMMUv3 Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 01/10] iommu: Fix comment for struct iommu_fwspec Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 02/10] iommu/arm-smmu-v3: Use device properties for pasid-num-bits Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 03/10] iommu: Separate IOMMU_DEV_FEAT_IOPF from IOMMU_DEV_FEAT_SVA Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 04/10] iommu/vt-d: Support IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-22 1:54 ` Lu Baolu
2021-01-21 12:36 ` [PATCH v10 05/10] uacce: Enable IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 06/10] iommu: Add a page fault handler Jean-Philippe Brucker
2021-01-21 12:36 ` [PATCH v10 07/10] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2021-01-22 10:35 ` Auger Eric
2021-01-21 12:36 ` Jean-Philippe Brucker [this message]
2021-01-21 12:36 ` [PATCH v10 09/10] ACPI/IORT: Enable stall support for platform devices Jean-Philippe Brucker
2021-01-21 18:57 ` Jonathan Cameron
2021-01-21 12:36 ` [PATCH v10 10/10] iommu/arm-smmu-v3: Add " Jean-Philippe Brucker
2021-01-21 19:12 ` Jonathan Cameron
2021-01-22 8:51 ` Jean-Philippe Brucker
2021-01-22 10:58 ` Jonathan Cameron
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