Hi All,
I am trying to modify the CXL persistent memory device, given at:
hw/mem/cxl_type3.c
to a volatile memory device.
I tried the following:
* In hw/cxl/cxl-mailbox-utils.c:
* changed the IDENTIFY_MEMORY_DEVICE mailbox handler to return
persistent capacity as 0, and expose entire memory as volatile.
* changed the IDENTIFY_MEMORY_DEVICE mailbox handler to indicate the
lba_size as 0 in the payload.
* In hw/mem/cxl_type3.c
* Changed function get_lsa_size to return 0.
* Changed function get_lsa to return 0.
* In the ct3_class_init function, changed the ps->class_id from
PCI_CLASS_STORAGE_EXPRESS to PCI_CLASS_MEMORY_RAM
* In the ct3_class_init function,
set_bit(DEVICE_CLASS_STORGE,dc->categories) was commented
* In the setup_cxl_memory function, ensured that the non-volatile flag
is false.
Still, when I boot this setup with Kernel 5.14, I see that the device shows up
as a persistent memory in /proc/iomem.
What else needs to be changed in the Qemu device and CXL model to support
volatile memory?
Is volatile memory Type 3 cxl device not supported in Qemu?
I use the following command:
../build/qemu-system-x86_64 -M q35,accel=kvm,nvdimm=on -m
8192M,slots=4,maxmem=40964M -smp 8,sockets=2,cores=2,threads=2 -hda
/lan/dscratch/singhabh/shradha/ubuntu-20.10-64_with_orig_driver_backup.qcow2
-enable-kvm -usbdevice tablet -L $VB_ROOT/etc/vm/common/ -object
memory-backend-file,id=cxl-mem1,share=on,mem-path=$PWD/cxl_type_mem,size=512M
-object
memory-backend-file,id=cxl-lsa,share=on,mem-path=$PWD/cxl_lsa_mem,size=2M
-device
"pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52,uid=0,len-window-base=1,window-base[0]=0x5c0000000,memdev[0]=cxl-mem1"
-device cxl-rp,id=rp0,bus=cxl.0,addr=0.0,chassis=0,slot=0 -device
cxl-type3,bus=rp0,memdev=cxl-mem1,id=cxl-pmem0,size=256M,lsa=cxl-lsa
Regards,
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Samarth Saxena
Sr Principal Software Engineer
T: +911204308300
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