Re: [RFC PATCH 0/3] QEMU ACPI generic port support

[Dave Jiang <dave.jiang@intel.com>]

On 5/3/23 3:42 AM, Jonathan Cameron wrote:
> On Tue, 18 Apr 2023 15:21:36 -0700
> Dave Jiang <dave.jiang@intel.com> wrote:
> 
>> s small RFC patch series is really a hack on what I need from qemu rather
>> than a proper implementation. I'm hoping to get some guidance from the list on
>> how to implement this correctly for qemu upstream. Thank you!
>>
>> The patch series provides support for the ACPI Generic Port support that's
>> defined by ACPI spec 6.5 5.2.16.7 (Generic Port Affinity Structure). The
>> series also adds a genport object that allows locality data to be injected via
>> qemu commandline to the HMAT tables. The generic port support is to allow a hot
>> plugged CXL memory device to calculate the locality data from the CPU to
>> the CXL device. The generic port related data provides the locality data from
>> the CPU to the CXL host bridge (latency and bandwidth). These data in
>> addition to the PCIe link data, CDAT from device, and CXL switch CDAT if switch
>> exist, provides the locality data for the entire path.
>>
>> Patch1: Adds Generic Port Affinity Structure sub-tables to the SRAT. For
>> each CXL Host Bridge (HB) a GPAS entry is created with a unique proximity
>> domain. For example, if the system is created with 4 proximity domains (PXM) for
>> system memory, then the next GPAS will get PXM 4 and so on.
> 
> I may be going crazy but I'm not seeing an increment on the numa node. So I think
> they all get 4 at the moment. Found it increment in patch 3.
> 
>>
>> Patch2: Add the json support for generic port. Split out because
>> clang-format really clobbers the json files.
>>
>> Patch3: Add a generic port object. The intention here is to allow setup of
>> numa nodes, add hmat-lb data and node distance for the generic targets. I had to
>> add a hack in qemu_create_cli_devices() to realize the genport objects. I need
>> guidance on where and how to do this properly so the genport objects
>> realize at the correct place and time.
>>
>> Example of genport setup:
>> -object genport,id=$X -numa node,genport=genport$X,nodeid=$Y,initiator=$Z
>> -numa hmat-lb,initiator=$Z,target=$X,hierarchy=memory,data-type=access-latency,latency=$latency
>> -numa hmat-lb,initiator=$Z,target=$X,hierarchy=memory,data-type=access-bandwidth,bandwidth=$bandwidthM
> 
> I think we should be using some links to the host bridges in here.
> So I don't think there should be an explicit genport object at all.
> Instead we should be able to point at the pxb itself.  Perhaps also
> allowing other port types in future.
> 
> Something like
> 
> -device pxb-cxl,id=cxl1.1
> -numa node,genport=cxl1.1,nodeid=$X
> -numa hmat-lb,initiator=$Z,target=$X,...
> -numa hmat-lb,initiator=$X,target=$Y,...
> //as generic port goes both ways.
> 
> As we are currently using bus_nr for UID (which is admittedly a somewhat dirty hack that
> just happened to be convenient) the ACPI building code can use that to fill in the SRAT
> entry at appropriate point.
> 
> I haven't tried implementing it so there may well be some ordering issues that
> require some late binding etc, but it should be possible to make it work.

Ok thanks for the suggestion Jonathan! I appreciate you looking over 
this. I'll take a look when I get a chance.

> 
>> for ((i = 0; i < total_nodes; i++)); do
>>          for ((j = 0; j < cxl_hbs; j++ )); do        # 2 CXL HBs
>>                  -numa dist,src=$i,dst=$X,val=$dist
>>          done
>> done
>> Linux kernel support:
>> https://lore.kernel.org/linux-cxl/168088732996.1441063.10107817505475386072.stgit@djiang5-mobl3/T/#t
>>
>> ---
>>
>> Dave Jiang (3):
>>        hw/acpi: Add support for Generic Port Affinity Structure to SRAT
>>        genport: Add json support for generic port
>>        acpi: add generic port device object
>>
>>
>>   hw/acpi/aml-build.c         | 21 +++++++++++++
>>   hw/acpi/genport.c           | 61 +++++++++++++++++++++++++++++++++++++
>>   hw/acpi/meson.build         |  1 +
>>   hw/i386/acpi-build.c        | 45 +++++++++++++++++++++++++++
>>   include/hw/acpi/aml-build.h | 27 ++++++++++++++++
>>   qapi/machine.json           |  3 +-
>>   qapi/qom.json               | 12 ++++++++
>>   softmmu/vl.c                | 26 ++++++++++++++++
>>   8 files changed, 195 insertions(+), 1 deletion(-)
>>   create mode 100644 hw/acpi/genport.c
>>
>> --
>>
>>
>