* Re: [PATCH] Documentation: CXL Maturity Map
2024-05-25 0:53 ` [PATCH] Documentation: CXL Maturity Map Dan Williams
@ 2024-06-06 3:23 ` Alison Schofield
2024-06-17 22:25 ` Davidlohr Bueso
2024-06-17 22:38 ` Dan Williams
2024-06-06 14:40 ` Jonathan Cameron
` (2 subsequent siblings)
3 siblings, 2 replies; 12+ messages in thread
From: Alison Schofield @ 2024-06-06 3:23 UTC (permalink / raw)
To: Dan Williams; +Cc: linux-cxl, dave.jiang, Jonathan.Cameron
On Fri, May 24, 2024 at 05:53:49PM -0700, Dan Williams wrote:
> Provide a survey of the work-in-progress maturity (implementation
> status) of various aspects of the CXL subsystem.
>
> Clarify that in addition to ongoing upkeep relative to specification
> updates, there are some long running themes in the driver that respond
> to the discovery of new corner cases (bugs) and new use cases (feature
> extensions).
>
> The primary audience is distribution maintainers, but it also serves as
> a guide for kernel developers to understand what aspects of the CXL
> subsystem need more help. It is a landing page to document ongoing
> progress, and a guide to discern exposure to work-in-progress features.
Hi Dan,
I'm wondering if Scan Media can be added to the list. I was within
striking distance of posting that set when higher priority work called.
Since it got pushed aside no one has cared :( I'd welcome the chance
to contribute it upstream if there is a justification. Can we add it
here as a [0] here to keep it on the radar.
-- Alison
>
> Help wanted / welcome to expand on the "Details" section.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Documentation/driver-api/cxl/index.rst | 2
> Documentation/driver-api/cxl/maturity-map.rst | 173 +++++++++++++++++++++++++
> MAINTAINERS | 1
> 3 files changed, 176 insertions(+)
> create mode 100644 Documentation/driver-api/cxl/maturity-map.rst
>
> diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
> index 036e49553542..12b82725d322 100644
> --- a/Documentation/driver-api/cxl/index.rst
> +++ b/Documentation/driver-api/cxl/index.rst
> @@ -9,4 +9,6 @@ Compute Express Link
>
> memory-devices
>
> + maturity-map
> +
> .. only:: subproject and html
> diff --git a/Documentation/driver-api/cxl/maturity-map.rst b/Documentation/driver-api/cxl/maturity-map.rst
> new file mode 100644
> index 000000000000..9c5bff6484dd
> --- /dev/null
> +++ b/Documentation/driver-api/cxl/maturity-map.rst
> @@ -0,0 +1,173 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
> +
> +===========================================
> +Compute Express Link Subsystem Maturity Map
> +===========================================
> +
> +The Linux CXL subsystem tracks the dynamic `CXL specification
> +<https://computeexpresslink.org/cxl-specification-landing-page>`_ that
> +continues to respond to new use cases with new features, capability
> +updates and fixes. At any given point some aspects of the subsystem are
> +more mature than others. While the periodic pull requests summarize the
> +`work being incorporated each merge window
> +<https://lore.kernel.org/linux-cxl/?q=s%3APULL+s%3ACXL+tc%3Atorvalds+NOT+s%3ARe>`_,
Thanks for the lore link!
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-06 3:23 ` Alison Schofield
@ 2024-06-17 22:25 ` Davidlohr Bueso
2024-06-17 22:38 ` Dan Williams
1 sibling, 0 replies; 12+ messages in thread
From: Davidlohr Bueso @ 2024-06-17 22:25 UTC (permalink / raw)
To: Alison Schofield
Cc: Dan Williams, linux-cxl, dave.jiang, Jonathan.Cameron,
a.manzanares
Hi Alison,
On Wed, 05 Jun 2024, Alison Schofield wrote:\n
>I'm wondering if Scan Media can be added to the list. I was within
>striking distance of posting that set when higher priority work called.
>Since it got pushed aside no one has cared :( I'd welcome the chance
>to contribute it upstream if there is a justification. Can we add it
>here as a [0] here to keep it on the radar.
I'd be interested in seeing these posted, and am curious as to what policy
you chose to use to trigger this. fyi there is support in Jonathan's qemu
newer branches for Scan Media, maybe that might serve you for any testing.
The kernel implementation I used to exercise the qemu changes was based
on poison list overflow, fwiw.
Thanks,
Davidlohr
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-06 3:23 ` Alison Schofield
2024-06-17 22:25 ` Davidlohr Bueso
@ 2024-06-17 22:38 ` Dan Williams
1 sibling, 0 replies; 12+ messages in thread
From: Dan Williams @ 2024-06-17 22:38 UTC (permalink / raw)
To: Alison Schofield, Dan Williams
Cc: linux-cxl, dave.jiang, Jonathan.Cameron, a.manzanares
Alison Schofield wrote:
> On Fri, May 24, 2024 at 05:53:49PM -0700, Dan Williams wrote:
> > Provide a survey of the work-in-progress maturity (implementation
> > status) of various aspects of the CXL subsystem.
> >
> > Clarify that in addition to ongoing upkeep relative to specification
> > updates, there are some long running themes in the driver that respond
> > to the discovery of new corner cases (bugs) and new use cases (feature
> > extensions).
> >
> > The primary audience is distribution maintainers, but it also serves as
> > a guide for kernel developers to understand what aspects of the CXL
> > subsystem need more help. It is a landing page to document ongoing
> > progress, and a guide to discern exposure to work-in-progress features.
>
> Hi Dan,
>
> I'm wondering if Scan Media can be added to the list. I was within
> striking distance of posting that set when higher priority work called.
> Since it got pushed aside no one has cared :( I'd welcome the chance
> to contribute it upstream if there is a justification. Can we add it
> here as a [0] here to keep it on the radar.
Added.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-05-25 0:53 ` [PATCH] Documentation: CXL Maturity Map Dan Williams
2024-06-06 3:23 ` Alison Schofield
@ 2024-06-06 14:40 ` Jonathan Cameron
2024-06-17 22:50 ` Dan Williams
2024-06-17 16:58 ` Adam Manzanares
2024-06-19 16:02 ` Alejandro Lucero Palau
3 siblings, 1 reply; 12+ messages in thread
From: Jonathan Cameron @ 2024-06-06 14:40 UTC (permalink / raw)
To: Dan Williams; +Cc: linux-cxl, dave.jiang, Adam Manzanares
On Fri, 24 May 2024 17:53:49 -0700
Dan Williams <dan.j.williams@intel.com> wrote:
> Provide a survey of the work-in-progress maturity (implementation
> status) of various aspects of the CXL subsystem.
>
> Clarify that in addition to ongoing upkeep relative to specification
> updates, there are some long running themes in the driver that respond
> to the discovery of new corner cases (bugs) and new use cases (feature
> extensions).
>
> The primary audience is distribution maintainers, but it also serves as
> a guide for kernel developers to understand what aspects of the CXL
> subsystem need more help. It is a landing page to document ongoing
> progress, and a guide to discern exposure to work-in-progress features.
>
> Help wanted / welcome to expand on the "Details" section.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This feels like a really bit opportunity for bikeshedding..
Ah well, a few comments inline. I've tried restrain my natural tendency
to argue about number assignments.
Adam's email address was garbled in my email client - fixed up.
> ---
> Documentation/driver-api/cxl/index.rst | 2
> Documentation/driver-api/cxl/maturity-map.rst | 173 +++++++++++++++++++++++++
> MAINTAINERS | 1
> 3 files changed, 176 insertions(+)
> create mode 100644 Documentation/driver-api/cxl/maturity-map.rst
>
> diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
> index 036e49553542..12b82725d322 100644
> --- a/Documentation/driver-api/cxl/index.rst
> +++ b/Documentation/driver-api/cxl/index.rst
> @@ -9,4 +9,6 @@ Compute Express Link
>
> memory-devices
>
> + maturity-map
> +
> .. only:: subproject and html
> diff --git a/Documentation/driver-api/cxl/maturity-map.rst b/Documentation/driver-api/cxl/maturity-map.rst
> new file mode 100644
> index 000000000000..9c5bff6484dd
> --- /dev/null
> +++ b/Documentation/driver-api/cxl/maturity-map.rst
> @@ -0,0 +1,173 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
> +
> +===========================================
> +Compute Express Link Subsystem Maturity Map
> +===========================================
> +
> +The Linux CXL subsystem tracks the dynamic `CXL specification
> +<https://computeexpresslink.org/cxl-specification-landing-page>`_ that
> +continues to respond to new use cases with new features, capability
> +updates and fixes. At any given point some aspects of the subsystem are
> +more mature than others. While the periodic pull requests summarize the
> +`work being incorporated each merge window
> +<https://lore.kernel.org/linux-cxl/?q=s%3APULL+s%3ACXL+tc%3Atorvalds+NOT+s%3ARe>`_,
> +those do not always convey progress relative to a starting point and a
> +future end goal.
> +
> +What follows is a coarse breakdown of the subsystem's major
> +responsibilities along with a maturity score. The expectation is that
> +the change-history of this document provides an overview summary of the
> +subsystem maturation over time.
> +
> +The maturity scores are:
> +
> +- [3] Mature: Work in this area is complete and no changes on the horizon.
> + Note that this score can regress from one kernel release to the next
> + based on new test results or end user reports.
> +
> +- [2] Stabilizing: Major functionality operational, common cases are
> + mature, but known corner cases are still a work in progress.
> +
> +- [1] Initial: Capability that has exited the Proof of Concept phase, but
> + may still have significant gaps to close and fixes to apply as real
> + world testing occurs.
> +
> +- [0] Known gap: Feature is on a medium to long term horizon to
> + implement. If the specification has a feature that does even have a '0'
> + score in this document, there is a good chance that no one in the
> + linux-cxl@vger.kernel.org community has started to look at it.
> +
> +- X: Out of scope for kernel enabling, or kernel enabling not required
> +
> +Feature and Capabilities
> +========================
> +
> +Enumeration / Provisioning
> +--------------------------
> +All of the fundamental enumeration an object model of the subsystem is
> +in place, but there are several corner cases that are pending closure.
> +
Feels like we should in passing mention that we support none of the
bits of CXL fabrics that are host visible (so mainly G-FAM I think).
[0] Fabrics / G-FAM (chapter 7)
[0] Global Access Enpoint
> +
> +* [2] CXL Window Enumeration
> +
> + * [0] :ref:`Extended-linear memory-side cache <extended-linear>`
> + * [0] Low Memory-hole
> + * [0] Hetero-interleave
> +
> +* [2] Switch Enumeration
> +
> + * [0] CXL register enumeration link-up dependency
> +
> +* [2] HDM Decoder Configuration
> +
> + * [0] Decoder target and granularity constraints
Feels like you added this one just so we can tick it off ;)
> +
> +2 Performance enumeration
> +
> + * [3] Endpoint CDAT
> + * [3] Switch CDAT
> + * [1] CDAT to Core-mm integration
[1] x86
[0] Arm64
[0] All other arch.
I guess could argue that's a core-mm problem, but the CEDT code
just all functions that are only implemented on x86.
> + * [1] Shared link
[0] Shared link. We've not merged that one yet though getting closer.
> +
> +* [2] Hotplug
> + (see CXL Window Enumeration)
> +
> + * [0] Handle Soft Reserved conflicts
> +
> +* [0] :ref:`RCH link status <rch-link-status>`
> +
> +RAS
> +---
> +In many ways CXL can be seen as a standardization of what would normally
> +be handled by custom EDAC drivers. The open development here is
> +mainly caused by the enumeration corner cases above.
> +
> +* [3] Component events (OS)
> +* [2] Component events (FFM)
> +* [1] Endpoint protocol errors (OS)
> +* [1] Endpoint protocol errors (FFM)
> +* [0] Switch protocol errors (OS)
> +* [1] Switch protocol errors (FFM)
> +* [2] DPA->HPA Address translation
> +
> + * [1] XOR Interleave translation
> + (see CXL Window Enumeration)
> +
> +* [1] Memory Failure coordination
> +* [0] Scrub control
[0] PPR
[0] Sparing
[0] Device built in test
> +* [2] ACPI error injection EINJ
> +
> + * [0] EINJ v2
> + * [X] Compliance DOE
> +
> +* [2] Native error injection
> +* [3] RCH error handling
> +* [1] VH error handling
> +
> +Mailbox commands
> +----------------
> +
> +* [3] Firmware update
> +* [3] Health / Alerts
> +* [1] :ref:`Background commands <background-commands>`
> +* [3] Santization
> +* [3] Security commands
> +* [3] RAW Command Debug Passthrough
> +* [0] CEL-only-validtion Passthrough
> +* [0] Switch CCI
> +* [3] Timestamp
> +* [1] PMU
Not mailbox, plus breakdown into switch vs type3 - see below.
> +* [1] PMEM labels
> +* [0] PMEM GPF / Dirty Shutdown
> +
PMU
---
[1] Type 3 PMU
[0] Switch USP/ DSP, Root Port
> +Security
> +--------
> +
> +* [X] CXL Trusted Execution Environment Security Protocol (TSP)
> +* [X] CXL IDE (subsumed by TSP)
> +
> +Multi-host memory
> +-----------------
> +
> +* [0] Dynamic Capacity Device Support
> +* [0] Sharing
Break this one up
Memory-pooling
--------------
[1] Hotplug of LDs (via PCI hotplug)
[0] Dynamic Capacity Device (DCD) Support
Multi-host sharing
------------------
Requires DCD support.
[0] Hardware coherent shared memory
[0] Software managed coherency shared memory
> +
> +Accelerator
> +-----------
> +
> +* [0] Accelerator memory enumeration HDM-D (CXL 1.1/2.0 Type-2)
> +* [0] Accelerator memory enumeration HDM-DB (CXL 3.0 Type-2)
> +* [0] CXL.cache 68b (CXL 2.0)
> +* [0] CXL.cache 256b Cache IDs (CXL 3.0)
> +
> +User Flow Support
> +-----------------
> +
> +* [0] HPA->DPA Address translation (need xormaps export solution)
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-06 14:40 ` Jonathan Cameron
@ 2024-06-17 22:50 ` Dan Williams
2024-06-20 17:45 ` Jonathan Cameron
0 siblings, 1 reply; 12+ messages in thread
From: Dan Williams @ 2024-06-17 22:50 UTC (permalink / raw)
To: Jonathan Cameron, Dan Williams; +Cc: linux-cxl, dave.jiang, Adam Manzanares
Jonathan Cameron wrote:
> On Fri, 24 May 2024 17:53:49 -0700
> Dan Williams <dan.j.williams@intel.com> wrote:
>
> > Provide a survey of the work-in-progress maturity (implementation
> > status) of various aspects of the CXL subsystem.
> >
> > Clarify that in addition to ongoing upkeep relative to specification
> > updates, there are some long running themes in the driver that respond
> > to the discovery of new corner cases (bugs) and new use cases (feature
> > extensions).
> >
> > The primary audience is distribution maintainers, but it also serves as
> > a guide for kernel developers to understand what aspects of the CXL
> > subsystem need more help. It is a landing page to document ongoing
> > progress, and a guide to discern exposure to work-in-progress features.
> >
> > Help wanted / welcome to expand on the "Details" section.
> >
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> This feels like a really bit opportunity for bikeshedding..
>
> Ah well, a few comments inline. I've tried restrain my natural tendency
> to argue about number assignments.
>
> Adam's email address was garbled in my email client - fixed up.
>
> > ---
> > Documentation/driver-api/cxl/index.rst | 2
> > Documentation/driver-api/cxl/maturity-map.rst | 173 +++++++++++++++++++++++++
> > MAINTAINERS | 1
> > 3 files changed, 176 insertions(+)
> > create mode 100644 Documentation/driver-api/cxl/maturity-map.rst
> >
> > diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
> > index 036e49553542..12b82725d322 100644
> > --- a/Documentation/driver-api/cxl/index.rst
> > +++ b/Documentation/driver-api/cxl/index.rst
> > @@ -9,4 +9,6 @@ Compute Express Link
> >
> > memory-devices
> >
> > + maturity-map
> > +
> > .. only:: subproject and html
> > diff --git a/Documentation/driver-api/cxl/maturity-map.rst b/Documentation/driver-api/cxl/maturity-map.rst
> > new file mode 100644
> > index 000000000000..9c5bff6484dd
> > --- /dev/null
> > +++ b/Documentation/driver-api/cxl/maturity-map.rst
> > @@ -0,0 +1,173 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +.. include:: <isonum.txt>
> > +
> > +===========================================
> > +Compute Express Link Subsystem Maturity Map
> > +===========================================
> > +
> > +The Linux CXL subsystem tracks the dynamic `CXL specification
> > +<https://computeexpresslink.org/cxl-specification-landing-page>`_ that
> > +continues to respond to new use cases with new features, capability
> > +updates and fixes. At any given point some aspects of the subsystem are
> > +more mature than others. While the periodic pull requests summarize the
> > +`work being incorporated each merge window
> > +<https://lore.kernel.org/linux-cxl/?q=s%3APULL+s%3ACXL+tc%3Atorvalds+NOT+s%3ARe>`_,
> > +those do not always convey progress relative to a starting point and a
> > +future end goal.
> > +
> > +What follows is a coarse breakdown of the subsystem's major
> > +responsibilities along with a maturity score. The expectation is that
> > +the change-history of this document provides an overview summary of the
> > +subsystem maturation over time.
> > +
> > +The maturity scores are:
> > +
> > +- [3] Mature: Work in this area is complete and no changes on the horizon.
> > + Note that this score can regress from one kernel release to the next
> > + based on new test results or end user reports.
> > +
> > +- [2] Stabilizing: Major functionality operational, common cases are
> > + mature, but known corner cases are still a work in progress.
> > +
> > +- [1] Initial: Capability that has exited the Proof of Concept phase, but
> > + may still have significant gaps to close and fixes to apply as real
> > + world testing occurs.
> > +
> > +- [0] Known gap: Feature is on a medium to long term horizon to
> > + implement. If the specification has a feature that does even have a '0'
> > + score in this document, there is a good chance that no one in the
> > + linux-cxl@vger.kernel.org community has started to look at it.
> > +
> > +- X: Out of scope for kernel enabling, or kernel enabling not required
> > +
> > +Feature and Capabilities
> > +========================
> > +
> > +Enumeration / Provisioning
> > +--------------------------
> > +All of the fundamental enumeration an object model of the subsystem is
> > +in place, but there are several corner cases that are pending closure.
> > +
>
> Feels like we should in passing mention that we support none of the
> bits of CXL fabrics that are host visible (so mainly G-FAM I think).
>
> [0] Fabrics / G-FAM (chapter 7)
> [0] Global Access Enpoint
Are those [0] or [X], not even sure what the kernel is expected to do with those?
> > +
> > +* [2] CXL Window Enumeration
> > +
> > + * [0] :ref:`Extended-linear memory-side cache <extended-linear>`
> > + * [0] Low Memory-hole
> > + * [0] Hetero-interleave
> > +
> > +* [2] Switch Enumeration
> > +
> > + * [0] CXL register enumeration link-up dependency
> > +
> > +* [2] HDM Decoder Configuration
> > +
> > + * [0] Decoder target and granularity constraints
>
> Feels like you added this one just so we can tick it off ;)
True, the list was a bit of brain dump. I also expect that "git log -p
Documentation/driver-api/cxl/maturity-map.rst" to show small edits like
this. No need to overthink this informal list.
> > +
> > +2 Performance enumeration
> > +
> > + * [3] Endpoint CDAT
> > + * [3] Switch CDAT
> > + * [1] CDAT to Core-mm integration
>
> [1] x86
> [0] Arm64
> [0] All other arch.
>
> I guess could argue that's a core-mm problem, but the CEDT code
> just all functions that are only implemented on x86.
Oh, good point, will add.
>
> > + * [1] Shared link
>
> [0] Shared link. We've not merged that one yet though getting closer.
Ok.
>
> > +
> > +* [2] Hotplug
> > + (see CXL Window Enumeration)
> > +
> > + * [0] Handle Soft Reserved conflicts
> > +
> > +* [0] :ref:`RCH link status <rch-link-status>`
> > +
> > +RAS
> > +---
> > +In many ways CXL can be seen as a standardization of what would normally
> > +be handled by custom EDAC drivers. The open development here is
> > +mainly caused by the enumeration corner cases above.
> > +
> > +* [3] Component events (OS)
> > +* [2] Component events (FFM)
> > +* [1] Endpoint protocol errors (OS)
> > +* [1] Endpoint protocol errors (FFM)
> > +* [0] Switch protocol errors (OS)
> > +* [1] Switch protocol errors (FFM)
> > +* [2] DPA->HPA Address translation
> > +
> > + * [1] XOR Interleave translation
> > + (see CXL Window Enumeration)
> > +
> > +* [1] Memory Failure coordination
> > +* [0] Scrub control
>
> [0] PPR
> [0] Sparing
> [0] Device built in test
Added.
>
> > +* [2] ACPI error injection EINJ
> > +
> > + * [0] EINJ v2
> > + * [X] Compliance DOE
> > +
> > +* [2] Native error injection
> > +* [3] RCH error handling
> > +* [1] VH error handling
> > +
> > +Mailbox commands
> > +----------------
> > +
> > +* [3] Firmware update
> > +* [3] Health / Alerts
> > +* [1] :ref:`Background commands <background-commands>`
> > +* [3] Santization
> > +* [3] Security commands
> > +* [3] RAW Command Debug Passthrough
> > +* [0] CEL-only-validtion Passthrough
> > +* [0] Switch CCI
> > +* [3] Timestamp
> > +* [1] PMU
>
> Not mailbox, plus breakdown into switch vs type3 - see below.
Done.
>
> > +* [1] PMEM labels
> > +* [0] PMEM GPF / Dirty Shutdown
> > +
>
> PMU
> ---
>
> [1] Type 3 PMU
> [0] Switch USP/ DSP, Root Port
...got it.
>
> > +Security
> > +--------
> > +
> > +* [X] CXL Trusted Execution Environment Security Protocol (TSP)
> > +* [X] CXL IDE (subsumed by TSP)
> > +
> > +Multi-host memory
> > +-----------------
> > +
> > +* [0] Dynamic Capacity Device Support
> > +* [0] Sharing
>
> Break this one up
>
> Memory-pooling
> --------------
>
> [1] Hotplug of LDs (via PCI hotplug)
> [0] Dynamic Capacity Device (DCD) Support
>
> Multi-host sharing
> ------------------
>
> Requires DCD support.
> [0] Hardware coherent shared memory
> [0] Software managed coherency shared memory
Looks good.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-17 22:50 ` Dan Williams
@ 2024-06-20 17:45 ` Jonathan Cameron
0 siblings, 0 replies; 12+ messages in thread
From: Jonathan Cameron @ 2024-06-20 17:45 UTC (permalink / raw)
To: Dan Williams; +Cc: linux-cxl, dave.jiang, Adam Manzanares
ling, or kernel enabling not required
> > > +
> > > +Feature and Capabilities
> > > +========================
> > > +
> > > +Enumeration / Provisioning
> > > +--------------------------
> > > +All of the fundamental enumeration an object model of the subsystem is
> > > +in place, but there are several corner cases that are pending closure.
> > > +
> >
> > Feels like we should in passing mention that we support none of the
> > bits of CXL fabrics that are host visible (so mainly G-FAM I think).
> >
> > [0] Fabrics / G-FAM (chapter 7)
> > [0] Global Access Enpoint
>
> Are those [0] or [X], not even sure what the kernel is expected to do with those?
I'm not 100% sure, but they are host programmable and there
are a bunch of more general structures to program that are
'kind of like' the hdm decoders with stuff like interleave
setup. So I think [0] but I've really not figure out the expected
software model for that stuff yet.
Jonathan
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-05-25 0:53 ` [PATCH] Documentation: CXL Maturity Map Dan Williams
2024-06-06 3:23 ` Alison Schofield
2024-06-06 14:40 ` Jonathan Cameron
@ 2024-06-17 16:58 ` Adam Manzanares
2024-06-17 22:54 ` Dan Williams
2024-06-19 16:02 ` Alejandro Lucero Palau
3 siblings, 1 reply; 12+ messages in thread
From: Adam Manzanares @ 2024-06-17 16:58 UTC (permalink / raw)
To: Dan Williams
Cc: linux-cxl@vger.kernel.org, dave.jiang@intel.com,
Jonathan.Cameron@huawei.com
On Fri, May 24, 2024 at 05:53:49PM -0700, Dan Williams wrote:
> Provide a survey of the work-in-progress maturity (implementation
> status) of various aspects of the CXL subsystem.
>
> Clarify that in addition to ongoing upkeep relative to specification
> updates, there are some long running themes in the driver that respond
> to the discovery of new corner cases (bugs) and new use cases (feature
> extensions).
>
> The primary audience is distribution maintainers, but it also serves as
> a guide for kernel developers to understand what aspects of the CXL
> subsystem need more help. It is a landing page to document ongoing
> progress, and a guide to discern exposure to work-in-progress features.
>
Thanks for putting this together Dan and thanks Jonathan for putting this
thread in my inbox.
> Help wanted / welcome to expand on the "Details" section.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Documentation/driver-api/cxl/index.rst | 2
> Documentation/driver-api/cxl/maturity-map.rst | 173 +++++++++++++++++++++++++
> MAINTAINERS | 1
> 3 files changed, 176 insertions(+)
> create mode 100644 Documentation/driver-api/cxl/maturity-map.rst
>
> diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
> index 036e49553542..12b82725d322 100644
> --- a/Documentation/driver-api/cxl/index.rst
> +++ b/Documentation/driver-api/cxl/index.rst
> @@ -9,4 +9,6 @@ Compute Express Link
>
> memory-devices
>
> + maturity-map
> +
> .. only:: subproject and html
> diff --git a/Documentation/driver-api/cxl/maturity-map.rst b/Documentation/driver-api/cxl/maturity-map.rst
> new file mode 100644
> index 000000000000..9c5bff6484dd
> --- /dev/null
> +++ b/Documentation/driver-api/cxl/maturity-map.rst
> @@ -0,0 +1,173 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
> +
> +===========================================
> +Compute Express Link Subsystem Maturity Map
> +===========================================
> +
> +The Linux CXL subsystem tracks the dynamic `CXL specification
> +<https://computeexpresslink.org/cxl-specification-landing-page>`_ that
> +continues to respond to new use cases with new features, capability
> +updates and fixes. At any given point some aspects of the subsystem are
> +more mature than others. While the periodic pull requests summarize the
> +`work being incorporated each merge window
> +<https://lore.kernel.org/linux-cxl/?q=s%3APULL+s%3ACXL+tc%3Atorvalds+NOT+s%3ARe>`_,
> +those do not always convey progress relative to a starting point and a
> +future end goal.
> +
> +What follows is a coarse breakdown of the subsystem's major
> +responsibilities along with a maturity score. The expectation is that
> +the change-history of this document provides an overview summary of the
> +subsystem maturation over time.
> +
> +The maturity scores are:
> +
> +- [3] Mature: Work in this area is complete and no changes on the horizon.
> + Note that this score can regress from one kernel release to the next
> + based on new test results or end user reports.
> +
> +- [2] Stabilizing: Major functionality operational, common cases are
> + mature, but known corner cases are still a work in progress.
> +
> +- [1] Initial: Capability that has exited the Proof of Concept phase, but
> + may still have significant gaps to close and fixes to apply as real
> + world testing occurs.
> +
> +- [0] Known gap: Feature is on a medium to long term horizon to
> + implement. If the specification has a feature that does even have a '0'
s/that does even have/that does not even have
> + score in this document, there is a good chance that no one in the
> + linux-cxl@vger.kernel.org community has started to look at it.
> +
> +- X: Out of scope for kernel enabling, or kernel enabling not required
> +
> +Feature and Capabilities
> +========================
> +
> +Enumeration / Provisioning
> +--------------------------
> +All of the fundamental enumeration an object model of the subsystem is
> +in place, but there are several corner cases that are pending closure.
> +
> +
> +* [2] CXL Window Enumeration
> +
> + * [0] :ref:`Extended-linear memory-side cache <extended-linear>`
> + * [0] Low Memory-hole
> + * [0] Hetero-interleave
> +
> +* [2] Switch Enumeration
> +
> + * [0] CXL register enumeration link-up dependency
> +
> +* [2] HDM Decoder Configuration
> +
> + * [0] Decoder target and granularity constraints
> +
> +2 Performance enumeration
> +
> + * [3] Endpoint CDAT
> + * [3] Switch CDAT
> + * [1] CDAT to Core-mm integration
> + * [1] Shared link
> +
> +* [2] Hotplug
> + (see CXL Window Enumeration)
> +
> + * [0] Handle Soft Reserved conflicts
> +
> +* [0] :ref:`RCH link status <rch-link-status>`
> +
> +RAS
> +---
> +In many ways CXL can be seen as a standardization of what would normally
> +be handled by custom EDAC drivers. The open development here is
> +mainly caused by the enumeration corner cases above.
> +
> +* [3] Component events (OS)
> +* [2] Component events (FFM)
> +* [1] Endpoint protocol errors (OS)
> +* [1] Endpoint protocol errors (FFM)
> +* [0] Switch protocol errors (OS)
> +* [1] Switch protocol errors (FFM)
> +* [2] DPA->HPA Address translation
> +
> + * [1] XOR Interleave translation
> + (see CXL Window Enumeration)
> +
> +* [1] Memory Failure coordination
> +* [0] Scrub control
> +* [2] ACPI error injection EINJ
> +
> + * [0] EINJ v2
> + * [X] Compliance DOE
> +
> +* [2] Native error injection
> +* [3] RCH error handling
> +* [1] VH error handling
> +
> +Mailbox commands
> +----------------
> +
> +* [3] Firmware update
> +* [3] Health / Alerts
> +* [1] :ref:`Background commands <background-commands>`
> +* [3] Santization
s/Santization/Sanitation
> +* [3] Security commands
> +* [3] RAW Command Debug Passthrough
> +* [0] CEL-only-validtion Passthrough
> +* [0] Switch CCI
> +* [3] Timestamp
> +* [1] PMU
> +* [1] PMEM labels
> +* [0] PMEM GPF / Dirty Shutdown
> +
> +Security
> +--------
> +
> +* [X] CXL Trusted Execution Environment Security Protocol (TSP)
> +* [X] CXL IDE (subsumed by TSP)
> +
> +Multi-host memory
> +-----------------
> +
> +* [0] Dynamic Capacity Device Support
> +* [0] Sharing
> +
> +Accelerator
> +-----------
> +
> +* [0] Accelerator memory enumeration HDM-D (CXL 1.1/2.0 Type-2)
> +* [0] Accelerator memory enumeration HDM-DB (CXL 3.0 Type-2)
> +* [0] CXL.cache 68b (CXL 2.0)
> +* [0] CXL.cache 256b Cache IDs (CXL 3.0)
> +
> +User Flow Support
> +-----------------
> +
> +* [0] HPA->DPA Address translation (need xormaps export solution)
> +
> +Details
> +=======
> +
> +.. _extended-linear:
> +
> +* **Extended-linear memory-side cache**: An HMAT proposal to enumerate the presence of a
> + memory-side cache where the cache capacity extends the SRAT address
> + range capacity. `See the ECN
> + <https://lore.kernel.org/linux-cxl/6650e4f835a0e_195e294a8@dwillia2-mobl3.amr.corp.intel.com.notmuch/>`_
> + for more details:
> +
> +.. _rch-link-status:
> +
> +* **RCH Link Status**: RCH (Restricted CXL Host) topologies, end up
> + hiding some standard registers like PCIe Link Status / Capabilities in
> + the CXL RCRB (Root Complex Register Block).
> +
> +.. _background-commands:
> +
> +* **Background commands**: The CXL background command mechanism is
> + awkward as the single slot is monopolized potentially indefinitely by
> + various commands. A `cancel on conflict
> + <http://lore.kernel.org/r/66035c2e8ba17_770232948b@dwillia2-xfh.jf.intel.com.notmuch>`_
> + facility is needed to make sure the kernel can ensure forward progress
> + of priority commands.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e533476081ba..d092b2ae5f25 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5331,6 +5331,7 @@ M: Ira Weiny <ira.weiny@intel.com>
> M: Dan Williams <dan.j.williams@intel.com>
> L: linux-cxl@vger.kernel.org
> S: Maintained
> +F: Documentation/driver-api/cxl
> F: drivers/cxl/
> F: include/linux/einj-cxl.h
> F: include/linux/cxl-event.h
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-17 16:58 ` Adam Manzanares
@ 2024-06-17 22:54 ` Dan Williams
2024-06-27 17:52 ` Adam Manzanares
0 siblings, 1 reply; 12+ messages in thread
From: Dan Williams @ 2024-06-17 22:54 UTC (permalink / raw)
To: Adam Manzanares, Dan Williams
Cc: linux-cxl@vger.kernel.org, dave.jiang@intel.com,
Jonathan.Cameron@huawei.com
Adam Manzanares wrote:
> On Fri, May 24, 2024 at 05:53:49PM -0700, Dan Williams wrote:
> > Provide a survey of the work-in-progress maturity (implementation
> > status) of various aspects of the CXL subsystem.
> >
> > Clarify that in addition to ongoing upkeep relative to specification
> > updates, there are some long running themes in the driver that respond
> > to the discovery of new corner cases (bugs) and new use cases (feature
> > extensions).
> >
> > The primary audience is distribution maintainers, but it also serves as
> > a guide for kernel developers to understand what aspects of the CXL
> > subsystem need more help. It is a landing page to document ongoing
> > progress, and a guide to discern exposure to work-in-progress features.
> >
[..]
> > +- [0] Known gap: Feature is on a medium to long term horizon to
> > + implement. If the specification has a feature that does even have a '0'
>
> s/that does even have/that does not even have
got it.
[..]
> > +Mailbox commands
> > +----------------
> > +
> > +* [3] Firmware update
> > +* [3] Health / Alerts
> > +* [1] :ref:`Background commands <background-commands>`
> > +* [3] Santization
>
> s/Santization/Sanitation
Hmm, no, "sanitation" appears nowhere in the spec.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-17 22:54 ` Dan Williams
@ 2024-06-27 17:52 ` Adam Manzanares
0 siblings, 0 replies; 12+ messages in thread
From: Adam Manzanares @ 2024-06-27 17:52 UTC (permalink / raw)
To: Dan Williams
Cc: linux-cxl@vger.kernel.org, dave.jiang@intel.com,
Jonathan.Cameron@huawei.com
On Mon, Jun 17, 2024 at 03:54:31PM -0700, Dan Williams wrote:
> Adam Manzanares wrote:
> > On Fri, May 24, 2024 at 05:53:49PM -0700, Dan Williams wrote:
> > > Provide a survey of the work-in-progress maturity (implementation
> > > status) of various aspects of the CXL subsystem.
> > >
> > > Clarify that in addition to ongoing upkeep relative to specification
> > > updates, there are some long running themes in the driver that respond
> > > to the discovery of new corner cases (bugs) and new use cases (feature
> > > extensions).
> > >
> > > The primary audience is distribution maintainers, but it also serves as
> > > a guide for kernel developers to understand what aspects of the CXL
> > > subsystem need more help. It is a landing page to document ongoing
> > > progress, and a guide to discern exposure to work-in-progress features.
> > >
> [..]
> > > +- [0] Known gap: Feature is on a medium to long term horizon to
> > > + implement. If the specification has a feature that does even have a '0'
> >
> > s/that does even have/that does not even have
>
> got it.
>
> [..]
> > > +Mailbox commands
> > > +----------------
> > > +
> > > +* [3] Firmware update
> > > +* [3] Health / Alerts
> > > +* [1] :ref:`Background commands <background-commands>`
> > > +* [3] Santization
> >
> > s/Santization/Sanitation
>
> Hmm, no, "sanitation" appears nowhere in the spec.
s/Santization/Sanitization
11.5.5.7.1
Feel free to add
Reviewed-by: Adam Manzanares <a.manzanares@samsung.com>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Documentation: CXL Maturity Map
2024-05-25 0:53 ` [PATCH] Documentation: CXL Maturity Map Dan Williams
` (2 preceding siblings ...)
2024-06-17 16:58 ` Adam Manzanares
@ 2024-06-19 16:02 ` Alejandro Lucero Palau
2024-07-03 23:26 ` Dan Williams
3 siblings, 1 reply; 12+ messages in thread
From: Alejandro Lucero Palau @ 2024-06-19 16:02 UTC (permalink / raw)
To: Dan Williams, linux-cxl; +Cc: dave.jiang, Jonathan.Cameron
Apologies for the late answer.
RAS is covered but what about how CXL/PCI devices are handled after a
slot reset?
I did expose my concern in that area when discussing the Type2 support
patchset, and if I'm not wrong this is not properly supported: nothing
for device detachment which should occur before the slot reset, nothing
for resume function after the slot reset. This is obviously more
important for Type2 devices and maybe not required for Type3.
On 5/25/24 01:53, Dan Williams wrote:
> Provide a survey of the work-in-progress maturity (implementation
> status) of various aspects of the CXL subsystem.
>
> Clarify that in addition to ongoing upkeep relative to specification
> updates, there are some long running themes in the driver that respond
> to the discovery of new corner cases (bugs) and new use cases (feature
> extensions).
>
> The primary audience is distribution maintainers, but it also serves as
> a guide for kernel developers to understand what aspects of the CXL
> subsystem need more help. It is a landing page to document ongoing
> progress, and a guide to discern exposure to work-in-progress features.
>
> Help wanted / welcome to expand on the "Details" section.
>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> Documentation/driver-api/cxl/index.rst | 2
> Documentation/driver-api/cxl/maturity-map.rst | 173 +++++++++++++++++++++++++
> MAINTAINERS | 1
> 3 files changed, 176 insertions(+)
> create mode 100644 Documentation/driver-api/cxl/maturity-map.rst
>
> diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
> index 036e49553542..12b82725d322 100644
> --- a/Documentation/driver-api/cxl/index.rst
> +++ b/Documentation/driver-api/cxl/index.rst
> @@ -9,4 +9,6 @@ Compute Express Link
>
> memory-devices
>
> + maturity-map
> +
> .. only:: subproject and html
> diff --git a/Documentation/driver-api/cxl/maturity-map.rst b/Documentation/driver-api/cxl/maturity-map.rst
> new file mode 100644
> index 000000000000..9c5bff6484dd
> --- /dev/null
> +++ b/Documentation/driver-api/cxl/maturity-map.rst
> @@ -0,0 +1,173 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
> +
> +===========================================
> +Compute Express Link Subsystem Maturity Map
> +===========================================
> +
> +The Linux CXL subsystem tracks the dynamic `CXL specification
> +<https://computeexpresslink.org/cxl-specification-landing-page>`_ that
> +continues to respond to new use cases with new features, capability
> +updates and fixes. At any given point some aspects of the subsystem are
> +more mature than others. While the periodic pull requests summarize the
> +`work being incorporated each merge window
> +<https://lore.kernel.org/linux-cxl/?q=s%3APULL+s%3ACXL+tc%3Atorvalds+NOT+s%3ARe>`_,
> +those do not always convey progress relative to a starting point and a
> +future end goal.
> +
> +What follows is a coarse breakdown of the subsystem's major
> +responsibilities along with a maturity score. The expectation is that
> +the change-history of this document provides an overview summary of the
> +subsystem maturation over time.
> +
> +The maturity scores are:
> +
> +- [3] Mature: Work in this area is complete and no changes on the horizon.
> + Note that this score can regress from one kernel release to the next
> + based on new test results or end user reports.
> +
> +- [2] Stabilizing: Major functionality operational, common cases are
> + mature, but known corner cases are still a work in progress.
> +
> +- [1] Initial: Capability that has exited the Proof of Concept phase, but
> + may still have significant gaps to close and fixes to apply as real
> + world testing occurs.
> +
> +- [0] Known gap: Feature is on a medium to long term horizon to
> + implement. If the specification has a feature that does even have a '0'
> + score in this document, there is a good chance that no one in the
> + linux-cxl@vger.kernel.org community has started to look at it.
> +
> +- X: Out of scope for kernel enabling, or kernel enabling not required
> +
> +Feature and Capabilities
> +========================
> +
> +Enumeration / Provisioning
> +--------------------------
> +All of the fundamental enumeration an object model of the subsystem is
> +in place, but there are several corner cases that are pending closure.
> +
> +
> +* [2] CXL Window Enumeration
> +
> + * [0] :ref:`Extended-linear memory-side cache <extended-linear>`
> + * [0] Low Memory-hole
> + * [0] Hetero-interleave
> +
> +* [2] Switch Enumeration
> +
> + * [0] CXL register enumeration link-up dependency
> +
> +* [2] HDM Decoder Configuration
> +
> + * [0] Decoder target and granularity constraints
> +
> +2 Performance enumeration
> +
> + * [3] Endpoint CDAT
> + * [3] Switch CDAT
> + * [1] CDAT to Core-mm integration
> + * [1] Shared link
> +
> +* [2] Hotplug
> + (see CXL Window Enumeration)
> +
> + * [0] Handle Soft Reserved conflicts
> +
> +* [0] :ref:`RCH link status <rch-link-status>`
> +
> +RAS
> +---
> +In many ways CXL can be seen as a standardization of what would normally
> +be handled by custom EDAC drivers. The open development here is
> +mainly caused by the enumeration corner cases above.
> +
> +* [3] Component events (OS)
> +* [2] Component events (FFM)
> +* [1] Endpoint protocol errors (OS)
> +* [1] Endpoint protocol errors (FFM)
> +* [0] Switch protocol errors (OS)
> +* [1] Switch protocol errors (FFM)
> +* [2] DPA->HPA Address translation
> +
> + * [1] XOR Interleave translation
> + (see CXL Window Enumeration)
> +
> +* [1] Memory Failure coordination
> +* [0] Scrub control
> +* [2] ACPI error injection EINJ
> +
> + * [0] EINJ v2
> + * [X] Compliance DOE
> +
> +* [2] Native error injection
> +* [3] RCH error handling
> +* [1] VH error handling
> +
> +Mailbox commands
> +----------------
> +
> +* [3] Firmware update
> +* [3] Health / Alerts
> +* [1] :ref:`Background commands <background-commands>`
> +* [3] Santization
> +* [3] Security commands
> +* [3] RAW Command Debug Passthrough
> +* [0] CEL-only-validtion Passthrough
> +* [0] Switch CCI
> +* [3] Timestamp
> +* [1] PMU
> +* [1] PMEM labels
> +* [0] PMEM GPF / Dirty Shutdown
> +
> +Security
> +--------
> +
> +* [X] CXL Trusted Execution Environment Security Protocol (TSP)
> +* [X] CXL IDE (subsumed by TSP)
> +
> +Multi-host memory
> +-----------------
> +
> +* [0] Dynamic Capacity Device Support
> +* [0] Sharing
> +
> +Accelerator
> +-----------
> +
> +* [0] Accelerator memory enumeration HDM-D (CXL 1.1/2.0 Type-2)
> +* [0] Accelerator memory enumeration HDM-DB (CXL 3.0 Type-2)
> +* [0] CXL.cache 68b (CXL 2.0)
> +* [0] CXL.cache 256b Cache IDs (CXL 3.0)
> +
> +User Flow Support
> +-----------------
> +
> +* [0] HPA->DPA Address translation (need xormaps export solution)
> +
> +Details
> +=======
> +
> +.. _extended-linear:
> +
> +* **Extended-linear memory-side cache**: An HMAT proposal to enumerate the presence of a
> + memory-side cache where the cache capacity extends the SRAT address
> + range capacity. `See the ECN
> + <https://lore.kernel.org/linux-cxl/6650e4f835a0e_195e294a8@dwillia2-mobl3.amr.corp.intel.com.notmuch/>`_
> + for more details:
> +
> +.. _rch-link-status:
> +
> +* **RCH Link Status**: RCH (Restricted CXL Host) topologies, end up
> + hiding some standard registers like PCIe Link Status / Capabilities in
> + the CXL RCRB (Root Complex Register Block).
> +
> +.. _background-commands:
> +
> +* **Background commands**: The CXL background command mechanism is
> + awkward as the single slot is monopolized potentially indefinitely by
> + various commands. A `cancel on conflict
> + <http://lore.kernel.org/r/66035c2e8ba17_770232948b@dwillia2-xfh.jf.intel.com.notmuch>`_
> + facility is needed to make sure the kernel can ensure forward progress
> + of priority commands.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e533476081ba..d092b2ae5f25 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5331,6 +5331,7 @@ M: Ira Weiny <ira.weiny@intel.com>
> M: Dan Williams <dan.j.williams@intel.com>
> L: linux-cxl@vger.kernel.org
> S: Maintained
> +F: Documentation/driver-api/cxl
> F: drivers/cxl/
> F: include/linux/einj-cxl.h
> F: include/linux/cxl-event.h
>
>
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH] Documentation: CXL Maturity Map
2024-06-19 16:02 ` Alejandro Lucero Palau
@ 2024-07-03 23:26 ` Dan Williams
0 siblings, 0 replies; 12+ messages in thread
From: Dan Williams @ 2024-07-03 23:26 UTC (permalink / raw)
To: Alejandro Lucero Palau, Dan Williams, linux-cxl
Cc: dave.jiang, Jonathan.Cameron
Alejandro Lucero Palau wrote:
> Apologies for the late answer.
>
>
> RAS is covered but what about how CXL/PCI devices are handled after a
> slot reset?
>
> I did expose my concern in that area when discussing the Type2 support
> patchset, and if I'm not wrong this is not properly supported: nothing
> for device detachment which should occur before the slot reset, nothing
> for resume function after the slot reset. This is obviously more
> important for Type2 devices and maybe not required for Type3.
Circling back to this as I go to post v2...
I think those type-2 RAS aspects are important, but it is not clear that
they are a concern of the CXL core. Endpoint drivers are enabled to get
pre and post reset notification via their registered 'struct
pci_error_handlers' operations. This maturity list is more targeted at
the CXL core infrastructure capabilities and type-2 drivers are going to
have their own localized maturity level.
I do need to go look more closely at your RAS assertions on that set. I
had otherwise been waiting a new posting with the sfc integration.
^ permalink raw reply [flat|nested] 12+ messages in thread