Re: [PATCH RFC 0/5] hw/cxl: Type 2 Device RFC

["Cédric Le Goater" <clg@redhat.com>]

Hello,

On 5/18/23 04:45, Ira Weiny wrote:
> Type 2 devices are not yet a reality.  Developing core kernel support
> is difficult without some test device to model against.
> 
> Define a type 2 device 'cxl-accel'.  This device is derived from the
> type 3 device and retains all that functionality for now.
> 
> Mock up a couple of accelerator features (Back Invalidate [BI] and
> Unordered IO [UIO]) as examples for the RFC.  These have no
> functionality other than to report the features as present for software
> to key off of.
> 
> Defining these devices in qemu can be done with the following example:
> 
> ...
>    -device cxl-accel,bus=sw0p0,volatile-memdev=cxl-ac-mem5,id=cxl-dev5,sn=0xCAFE0005
> ...
> 
> NOTE: I'm leaving off Michael Tsirkin for now because this is really
> rough and I'm mainly sending it out because it was talked about in the
> CXL community call on 5/16.
> 
> Not-Yet-Signed-off-by: Ira Weiny <ira.weiny@intel.com>


A recent proposal to add support in VFIO for CXL passthrough uses
this emulated device and a sample driver for a proof of concept.
For this effort, it would be very useful to have a QEMU model for
a CXL type2 device, even partially implemented.

I haven't found any updates of this series. What are the plans for
upstream today ?

For vfio-cxl, see :
   
* [RFC] vfio: introduce vfio-cxl to support CXL type-2 accelerator passthrough
   https://lore.kernel.org/kvm/20240920223446.1908673-1-zhiw@nvidia.com
* [RFC] Introduce vfio-cxl to support CXL type-2 device passthrough
   https://lore.kernel.org/all/20240921071440.1915876-1-zhiw@nvidia.com/


Thanks,

C.

   

> ---
> Ira Weiny (5):
>        hw/cxl: Use define for build bug detection
>        hw/cxl: Refactor component register initialization
>        hw/cxl: Derive a CXL accelerator device from Type-3
>        hw/cxl/accel: Add Back-Invalidate decoder capbility structure
>        hw/cxl: Add UIO HDM decoder register fields
> 
>   docs/system/devices/cxl.rst    | 11 ++++++
>   hw/cxl/cxl-component-utils.c   | 80 +++++++++++++++++++-----------------------
>   hw/mem/cxl_type3.c             | 39 ++++++++++++++++++++
>   include/hw/cxl/cxl_component.h | 51 +++++++++++++++++++--------
>   include/hw/cxl/cxl_device.h    | 16 +++++++++
>   include/hw/pci/pci_ids.h       |  1 +
>   6 files changed, 141 insertions(+), 57 deletions(-)
> ---
> base-commit: 8eb2a03258313f404ca0c8609a8f9009b9b4318c
> change-id: 20230517-rfc-type2-dev-c2d661a29d96
> 
> Best regards,