From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: joro@8bytes.org, will@kernel.org
Cc: vivek.gautam@arm.com, guohanjun@huawei.com,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
linux-acpi@vger.kernel.org, zhangfei.gao@linaro.org,
lenb@kernel.org, devicetree@vger.kernel.org,
kevin.tian@intel.com, Rob Herring <robh@kernel.org>,
robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org,
rjw@rjwysocki.net, iommu@lists.linux-foundation.org,
sudeep.holla@arm.com, robin.murphy@arm.com,
linux-accelerators@lists.ozlabs.org
Subject: [PATCH v12 08/10] dt-bindings: document stall property for IOMMU masters
Date: Wed, 27 Jan 2021 16:43:21 +0100 [thread overview]
Message-ID: <20210127154322.3959196-9-jean-philippe@linaro.org> (raw)
In-Reply-To: <20210127154322.3959196-1-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
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-01-27 15:44 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 15:43 [PATCH v12 00/10] iommu: I/O page faults for SMMUv3 Jean-Philippe Brucker
2021-01-27 15:43 ` [PATCH v12 01/10] iommu: Fix comment for struct iommu_fwspec Jean-Philippe Brucker
2021-01-27 15:43 ` [PATCH v12 02/10] iommu/arm-smmu-v3: Use device properties for pasid-num-bits Jean-Philippe Brucker
2021-02-01 7:30 ` Auger Eric
2021-01-27 15:43 ` [PATCH v12 03/10] iommu: Separate IOMMU_DEV_FEAT_IOPF from IOMMU_DEV_FEAT_SVA Jean-Philippe Brucker
2021-02-01 7:35 ` Auger Eric
2021-01-27 15:43 ` [PATCH v12 04/10] iommu/vt-d: Support IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-27 15:43 ` [PATCH v12 05/10] uacce: Enable IOMMU_DEV_FEAT_IOPF Jean-Philippe Brucker
2021-01-27 15:43 ` [PATCH v12 06/10] iommu: Add a page fault handler Jean-Philippe Brucker
2021-01-31 18:29 ` Auger Eric
2021-02-02 5:51 ` Shenming Lu
2021-01-27 15:43 ` [PATCH v12 07/10] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2021-01-27 15:43 ` Jean-Philippe Brucker [this message]
2021-02-01 7:28 ` [PATCH v12 08/10] dt-bindings: document stall property for IOMMU masters Auger Eric
2021-01-27 15:43 ` [PATCH v12 09/10] ACPI/IORT: Enable stall support for platform devices Jean-Philippe Brucker
2021-01-27 15:43 ` [PATCH v12 10/10] iommu/arm-smmu-v3: Add " Jean-Philippe Brucker
2021-01-31 18:29 ` Auger Eric
2021-02-01 11:12 ` Jean-Philippe Brucker
2021-02-01 13:16 ` Auger Eric
2021-02-01 15:19 ` Jean-Philippe Brucker
2021-02-01 1:18 ` Zhou Wang
2021-02-01 11:14 ` Jean-Philippe Brucker
2021-02-01 12:53 ` Zhou Wang
2021-02-26 9:43 ` Zhou Wang
2021-02-26 16:29 ` Jean-Philippe Brucker
2021-02-27 3:40 ` Zhou Wang
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