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Re: [PATCH v3 2/2] hw/cxl: Multi-Region CXL Type-3 Devices (Volatile and


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v3 2/2] hw/cxl: Multi-Region CXL Type-3 Devices (Volatile and Persistent)
Date: Tue, 21 Feb 2023 23:33:14 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.8.0

On 21/2/23 15:00, Jonathan Cameron wrote:
From: Gregory Price <gourry.memverge@gmail.com>

This commit enables each CXL Type-3 device to contain one volatile
memory region and one persistent region.

Two new properties have been added to cxl-type3 device initialization:
     [volatile-memdev] and [persistent-memdev]

The existing [memdev] property has been deprecated and will default the
memory region to a persistent memory region (although a user may assign
the region to a ram or file backed region). It cannot be used in
combination with the new [persistent-memdev] property.

Partitioning volatile memory from persistent memory is not yet supported.

Volatile memory is mapped at DPA(0x0), while Persistent memory is mapped
at DPA(vmem->size), per CXL Spec 8.2.9.8.2.0 - Get Partition Info.

Signed-off-by: Gregory Price <gregory.price@memverge.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

---
v3:
- Don't set the DVSEC range register base address
v2:
- Fixed an off by one in address space selection.
- Gather tags.
---
  docs/system/devices/cxl.rst    |  49 ++++--
  hw/cxl/cxl-mailbox-utils.c     |  26 +--
  hw/mem/cxl_type3.c             | 294 +++++++++++++++++++++++++--------
  include/hw/cxl/cxl_device.h    |  11 +-
  tests/qtest/bios-tables-test.c |   8 +-
  tests/qtest/cxl-test.c         |  76 +++++++--
  6 files changed, 353 insertions(+), 111 deletions(-)

diff --git a/docs/system/devices/cxl.rst b/docs/system/devices/cxl.rst
index f25783a4ec..89a41cff73 100644
--- a/docs/system/devices/cxl.rst
+++ b/docs/system/devices/cxl.rst
@@ -300,7 +300,7 @@ Example topology involving a switch::
Example command lines
  ---------------------
-A very simple setup with just one directly attached CXL Type 3 device::
+A very simple setup with just one directly attached CXL Type 3 Persistent 
Memory device::
qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 -cpu max \
    ...
@@ -308,7 +308,28 @@ A very simple setup with just one directly attached CXL 
Type 3 device::
    -object 
memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/lsa.raw,size=256M \
    -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
    -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
-  -device cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0 \
+  -device 
cxl-type3,bus=root_port13,persistent-memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0 \
+  -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G
+
+A very simple setup with just one directly attached CXL Type 3 Volatile Memory 
device::
+
+  qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 
-cpu max \
+  ...
+  -object memory-backend-ram,id=vmem0,share=on,size=256M \
+  -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
+  -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
+  -device cxl-type3,bus=root_port13,volatile-memdev=vmem0,id=cxl-vmem0 \
+  -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G
+
+The same volatile setup may optionally include an LSA region::
+
+  qemu-system-aarch64 -M virt,gic-version=3,cxl=on -m 4g,maxmem=8G,slots=8 
-cpu max \
+  ...
+  -object memory-backend-ram,id=vmem0,share=on,size=256M \
+  -object 
memory-backend-file,id=cxl-lsa0,share=on,mem-path=/tmp/lsa.raw,size=256M \
+  -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
+  -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
+  -device 
cxl-type3,bus=root_port13,volatile-memdev=vmem0,lsa=cxl-lsa0,id=cxl-vmem0 \
    -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G
A setup suitable for 4 way interleave. Only one fixed window provided, to enable 2 way
@@ -328,13 +349,13 @@ the CXL Type3 device directly attached (no switches).::
    -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
    -device pxb-cxl,bus_nr=222,bus=pcie.0,id=cxl.2 \
    -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
-  -device cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0 \
+  -device 
cxl-type3,bus=root_port13,persistent-memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0 \
    -device cxl-rp,port=1,bus=cxl.1,id=root_port14,chassis=0,slot=3 \
-  -device cxl-type3,bus=root_port14,memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem1 \
+  -device 
cxl-type3,bus=root_port14,persistent-memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem1 \
    -device cxl-rp,port=0,bus=cxl.2,id=root_port15,chassis=0,slot=5 \
-  -device cxl-type3,bus=root_port15,memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem2 \
+  -device 
cxl-type3,bus=root_port15,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem2 \
    -device cxl-rp,port=1,bus=cxl.2,id=root_port16,chassis=0,slot=6 \
-  -device cxl-type3,bus=root_port16,memdev=cxl-mem4,lsa=cxl-lsa4,id=cxl-pmem3 \
+  -device 
cxl-type3,bus=root_port16,persistent-memdev=cxl-mem4,lsa=cxl-lsa4,id=cxl-pmem3 \
    -M 
cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.targets.1=cxl.2,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=8k
An example of 4 devices below a switch suitable for 1, 2 or 4 way interleave::
@@ -354,15 +375,23 @@ An example of 4 devices below a switch suitable for 1, 2 
or 4 way interleave::
    -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
    -device cxl-upstream,bus=root_port0,id=us0 \
    -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
-  -device 
cxl-type3,bus=swport0,memdev=cxl-mem0,lsa=cxl-lsa0,id=cxl-pmem0,size=256M \
+  -device 
cxl-type3,bus=swport0,persistent-memdev=cxl-mem0,lsa=cxl-lsa0,id=cxl-pmem0,size=256M
 \
    -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
-  -device 
cxl-type3,bus=swport1,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem1,size=256M \
+  -device 
cxl-type3,bus=swport1,persistent-memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem1,size=256M
 \
    -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
-  -device 
cxl-type3,bus=swport2,memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem2,size=256M \
+  -device 
cxl-type3,bus=swport2,persistent-memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem2,size=256M
 \
    -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
-  -device 
cxl-type3,bus=swport3,memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,size=256M \
+  -device 
cxl-type3,bus=swport3,persistent-memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem3,size=256M
 \
    -M 
cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=4k
+Deprecations
+------------
+
+The Type 3 device [memdev] attribute has been deprecated in favor of the
+[persistent-memdev] attributes. [memdev] will default to a persistent memory
+device for backward compatibility and is incapable of being used in combination
+with [persistent-memdev].
+

Probably worth mentioning & referring this in docs/about/deprecated.rst.



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