Re: [PATCH 0/5] Multi-Region and Volatile Memory support for CXL Type-3 Devices

[Michael S. Tsirkin]

On Tue, Oct 11, 2022 at 05:19:11PM -0400, Gregory Price wrote:
> Summary of Changes:
> 1) Correction of PCI_CLASS from STORAGE_EXPRESS to MEMORY_CXL on init
> 2) Add CXL_CAPACITY_MULTIPLIER definition to replace magic numbers
> 3) Refactor CDAT DSMAS Initialization for multi-region initialization
> 4) Multi-Region and Volatile Memory support for CXL Type-3 Devices
> 5) Test and Documentation updates
> 
> Developed with input from Jonathan Cameron and Davidloh Bueso.
> 
> This series brings 2 features to CXL Type-3 Devices:
>     1) Volatile Memory Region support
>     2) Multi-Region support (1 Volatile, 1 Persistent)
> 
> In this series we implement multi-region and volatile region support
> through 6 major changes to CXL devices
>     1) The HostMemoryBackend [hostmem] has been replaced by two
>        [hostvmem] and [hostpmem] to store volatile and persistent memory
>        respectively
>     2) The single AddressSpace has been replaced by two AddressSpaces
>        [hostvmem_as] and [hostpmem_as] to map respective memdevs.
>     3) Each memory region size and total region are stored separately
>     4) The CDAT and DVSEC memory map entries have been updated:
>        a) if vmem is present, vmem is mapped at DPA(0)
>        b) if pmem is present
>           i)  and vmem is present, pmem is mapped at DPA(vmem->size)
>           ii) else, pmem is mapped at DPA(0)
>        c) partitioning of pmem is not supported in this patch set but
>           has been discussed and this design should suffice.
>     5) Read/Write functions have been updated to access AddressSpaces
>        according to the mapping described in #4
>     6) cxl-mailbox has been updated to report the respective size of
>        volatile and persistent memory regions
> 
> CXL Spec (3.0) Section 8.2.9.8.2.0 - Get Partition Info
>   Active Volatile Memory
>     The device shall provide this volatile capacity starting at DPA 0
>   Active Persistent Memory
>     The device shall provide this persistent capacity starting at the
>     DPA immediately following the volatile capacity
> 
> Partitioning of Persistent Memory regions may be supported on following
> patch sets.
> 
> Submitted as an extention to the CDAT emulation because the CDAT DSMAS
> entry concerns memory mapping and is required to successfully map memory
> regions correctly in bios/efi.

As there will be v8 of CDAT patches I expect there will be a rebase
of this patchset too.

> Gregory Price (5):
>   hw/cxl: set cxl-type3 device type to PCI_CLASS_MEMORY_CXL
>   hw/cxl: Add CXL_CAPACITY_MULTIPLIER definition
>   hw/mem/cxl_type: Generalize CDATDsmas initialization for Memory
>     Regions
>   hw/cxl: Multi-Region CXL Type-3 Devices (Volatile and Persistent)
>   cxl: update tests and documentation for new cxl properties
> 
>  docs/system/devices/cxl.rst |  53 ++++-
>  hw/cxl/cxl-mailbox-utils.c  |  23 +-
>  hw/mem/cxl_type3.c          | 449 +++++++++++++++++++++++-------------
>  include/hw/cxl/cxl_device.h |  11 +-
>  tests/qtest/cxl-test.c      |  81 ++++++-
>  5 files changed, 416 insertions(+), 201 deletions(-)
> 
> -- 
> 2.37.3