Re: [PATCH v2 04/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing)

2020-06-15 Thread Fenghua Yu
Hi, Baolu,

On Sat, Jun 13, 2020 at 08:17:40PM +0800, Lu Baolu wrote:
> Hi Fenghua,
> 
> On 2020/6/13 8:41, Fenghua Yu wrote:
> >+implement implement fairness or ensure forward progress can be made.
> 
> Repeated "implement".

Will fix this.

> >+For example, the Intel Data Streaming Accelerator (DSA) uses
> >+intel_svm_bind_mm(), which will do the following.
> 
> The Intel SVM APIs have been deprecated. Drivers should use
> iommu_sva_bind_device() instead. Please also update other places in
> this document.

Will fix this.

Thanks.

-Fenghua



Re: [PATCH v2 04/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing)

2020-06-13 Thread Lu Baolu

Hi Fenghua,

On 2020/6/13 8:41, Fenghua Yu wrote:

From: Ashok Raj 

ENQCMD and Data Streaming Accelerator (DSA) and all of their associated
features are a complicated stack with lots of interconnected pieces.
This documentation provides a big picture overview for all of the
features.

Signed-off-by: Ashok Raj 
Co-developed-by: Fenghua Yu 
Signed-off-by: Fenghua Yu 
Reviewed-by: Tony Luck 
---
v2:
- Fix the doc format and add the doc in toctree (Thomas)
- Modify the doc for better description (Thomas, Tony, Dave)

  Documentation/x86/index.rst |   1 +
  Documentation/x86/sva.rst   | 287 
  2 files changed, 288 insertions(+)
  create mode 100644 Documentation/x86/sva.rst

diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index 265d9e9a093b..e5d5ff096685 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -30,3 +30,4 @@ x86-specific Documentation
 usb-legacy-support
 i386/index
 x86_64/index
+   sva
diff --git a/Documentation/x86/sva.rst b/Documentation/x86/sva.rst
new file mode 100644
index ..1e52208c7dda
--- /dev/null
+++ b/Documentation/x86/sva.rst
@@ -0,0 +1,287 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===
+Shared Virtual Addressing (SVA) with ENQCMD
+===
+
+Background
+==
+
+Shared Virtual Addressing (SVA) allows the processor and device to use the
+same virtual addresses avoiding the need for software to translate virtual
+addresses to physical addresses. SVA is what PCIe calls Shared Virtual
+Memory (SVM)
+
+In addition to the convenience of using application virtual addresses
+by the device, it also doesn't require pinning pages for DMA.
+PCIe Address Translation Services (ATS) along with Page Request Interface
+(PRI) allow devices to function much the same way as the CPU handling
+application page-faults. For more information please refer to PCIe
+specification Chapter 10: ATS Specification.
+
+Use of SVA requires IOMMU support in the platform. IOMMU also is required
+to support PCIe features ATS and PRI. ATS allows devices to cache
+translations for the virtual address. IOMMU driver uses the mmu_notifier()
+support to keep the device tlb cache and the CPU cache in sync. PRI allows
+the device to request paging the virtual address before using if they are
+not paged in the CPU page tables.
+
+
+Shared Hardware Workqueues
+==
+
+Unlike Single Root I/O Virtualization (SRIOV), Scalable IOV (SIOV) permits
+the use of Shared Work Queues (SWQ) by both applications and Virtual
+Machines (VM's). This allows better hardware utilization vs. hard
+partitioning resources that could result in under utilization. In order to
+allow the hardware to distinguish the context for which work is being
+executed in the hardware by SWQ interface, SIOV uses Process Address Space
+ID (PASID), which is a 20bit number defined by the PCIe SIG.
+
+PASID value is encoded in all transactions from the device. This allows the
+IOMMU to track I/O on a per-PASID granularity in addition to using the PCIe
+Resource Identifier (RID) which is the Bus/Device/Function.
+
+
+ENQCMD
+==
+
+ENQCMD is a new instruction on Intel platforms that atomically submits a
+work descriptor to a device. The descriptor includes the operation to be
+performed, virtual addresses of all parameters, virtual address of a completion
+record, and the PASID (process address space ID) of the current process.
+
+ENQCMD works with non-posted semantics and carries a status back if the
+command was accepted by hardware. This allows the submitter to know if the
+submission needs to be retried or other device specific mechanisms to
+implement implement fairness or ensure forward progress can be made.


Repeated "implement".


+
+ENQCMD is the glue that ensures applications can directly submit commands
+to the hardware and also permit hardware to be aware of application context
+to perform I/O operations via use of PASID.
+
+Process Address Space Tagging
+=
+
+A new thread scoped MSR (IA32_PASID) provides the connection between
+user processes and the rest of the hardware. When an application first
+accesses an SVA capable device this MSR is initialized with a newly
+allocated PASID. The driver for the device calls an IOMMU specific api
+that sets up the routing for DMA and page-requests.
+
+For example, the Intel Data Streaming Accelerator (DSA) uses
+intel_svm_bind_mm(), which will do the following.


The Intel SVM APIs have been deprecated. Drivers should use
iommu_sva_bind_device() instead. Please also update other places in
this document.


+
+- Allocate the PASID, and program the process page-table (cr3) in the PASID
+  context entries.
+- Register for mmu_notifier() to track any page-table invalidations to keep
+  the device tlb in sync. For example, when a page-table entry is invalidated,
+  IOMMU propagates the 

[PATCH v2 04/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing)

2020-06-12 Thread Fenghua Yu
From: Ashok Raj 

ENQCMD and Data Streaming Accelerator (DSA) and all of their associated
features are a complicated stack with lots of interconnected pieces.
This documentation provides a big picture overview for all of the
features.

Signed-off-by: Ashok Raj 
Co-developed-by: Fenghua Yu 
Signed-off-by: Fenghua Yu 
Reviewed-by: Tony Luck 
---
v2:
- Fix the doc format and add the doc in toctree (Thomas)
- Modify the doc for better description (Thomas, Tony, Dave)

 Documentation/x86/index.rst |   1 +
 Documentation/x86/sva.rst   | 287 
 2 files changed, 288 insertions(+)
 create mode 100644 Documentation/x86/sva.rst

diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst
index 265d9e9a093b..e5d5ff096685 100644
--- a/Documentation/x86/index.rst
+++ b/Documentation/x86/index.rst
@@ -30,3 +30,4 @@ x86-specific Documentation
usb-legacy-support
i386/index
x86_64/index
+   sva
diff --git a/Documentation/x86/sva.rst b/Documentation/x86/sva.rst
new file mode 100644
index ..1e52208c7dda
--- /dev/null
+++ b/Documentation/x86/sva.rst
@@ -0,0 +1,287 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===
+Shared Virtual Addressing (SVA) with ENQCMD
+===
+
+Background
+==
+
+Shared Virtual Addressing (SVA) allows the processor and device to use the
+same virtual addresses avoiding the need for software to translate virtual
+addresses to physical addresses. SVA is what PCIe calls Shared Virtual
+Memory (SVM)
+
+In addition to the convenience of using application virtual addresses
+by the device, it also doesn't require pinning pages for DMA.
+PCIe Address Translation Services (ATS) along with Page Request Interface
+(PRI) allow devices to function much the same way as the CPU handling
+application page-faults. For more information please refer to PCIe
+specification Chapter 10: ATS Specification.
+
+Use of SVA requires IOMMU support in the platform. IOMMU also is required
+to support PCIe features ATS and PRI. ATS allows devices to cache
+translations for the virtual address. IOMMU driver uses the mmu_notifier()
+support to keep the device tlb cache and the CPU cache in sync. PRI allows
+the device to request paging the virtual address before using if they are
+not paged in the CPU page tables.
+
+
+Shared Hardware Workqueues
+==
+
+Unlike Single Root I/O Virtualization (SRIOV), Scalable IOV (SIOV) permits
+the use of Shared Work Queues (SWQ) by both applications and Virtual
+Machines (VM's). This allows better hardware utilization vs. hard
+partitioning resources that could result in under utilization. In order to
+allow the hardware to distinguish the context for which work is being
+executed in the hardware by SWQ interface, SIOV uses Process Address Space
+ID (PASID), which is a 20bit number defined by the PCIe SIG.
+
+PASID value is encoded in all transactions from the device. This allows the
+IOMMU to track I/O on a per-PASID granularity in addition to using the PCIe
+Resource Identifier (RID) which is the Bus/Device/Function.
+
+
+ENQCMD
+==
+
+ENQCMD is a new instruction on Intel platforms that atomically submits a
+work descriptor to a device. The descriptor includes the operation to be
+performed, virtual addresses of all parameters, virtual address of a completion
+record, and the PASID (process address space ID) of the current process.
+
+ENQCMD works with non-posted semantics and carries a status back if the
+command was accepted by hardware. This allows the submitter to know if the
+submission needs to be retried or other device specific mechanisms to
+implement implement fairness or ensure forward progress can be made.
+
+ENQCMD is the glue that ensures applications can directly submit commands
+to the hardware and also permit hardware to be aware of application context
+to perform I/O operations via use of PASID.
+
+Process Address Space Tagging
+=
+
+A new thread scoped MSR (IA32_PASID) provides the connection between
+user processes and the rest of the hardware. When an application first
+accesses an SVA capable device this MSR is initialized with a newly
+allocated PASID. The driver for the device calls an IOMMU specific api
+that sets up the routing for DMA and page-requests.
+
+For example, the Intel Data Streaming Accelerator (DSA) uses
+intel_svm_bind_mm(), which will do the following.
+
+- Allocate the PASID, and program the process page-table (cr3) in the PASID
+  context entries.
+- Register for mmu_notifier() to track any page-table invalidations to keep
+  the device tlb in sync. For example, when a page-table entry is invalidated,
+  IOMMU propagates the invalidation to device tlb. This will force any
+  future access by the device to this virtual address to participate in
+  ATS. If the IOMMU responds with proper response that a page is not
+  present, the device would request the