Re: [PATCH 00/18] CXL RAM and the 'Soft Reserved' => 'System RAM' default

[Gregory Price <gregory.price@memverge.com>]

On Sun, Feb 05, 2023 at 05:02:29PM -0800, Dan Williams wrote:
> Summary:
> --------
> 
> CXL RAM support allows for the dynamic provisioning of new CXL RAM
> regions, and more routinely, assembling a region from an existing
> configuration established by platform-firmware. The latter is motivated
> by CXL memory RAS (Reliability, Availability and Serviceability)
> support, that requires associating device events with System Physical
> Address ranges and vice versa.
> 
> The 'Soft Reserved' policy rework arranges for performance
> differentiated memory like CXL attached DRAM, or high-bandwidth memory,
> to be designated for 'System RAM' by default, rather than the device-dax
> dedicated access mode. That current device-dax default is confusing and
> surprising for the Pareto of users that do not expect memory to be
> quarantined for dedicated access by default. Most users expect all
> 'System RAM'-capable memory to show up in FREE(1).

Leverage the same QEMU branch, machine, and configuration as my prior
tests, i'm now experiencing a kernel panic on boot.  Will debug a bit
in the morning, but here is the stack trace i'm seeing

Saw this in both 1 and 2 root port configurations

(note: I also have the region reset issue previously discussed on top of
your branch).  

QEMU configuration:

sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \
-drive file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd \
-m 2G,slots=4,maxmem=4G \
-smp 4 \
-machine type=q35,accel=kvm,cxl=on \
-enable-kvm \
-nographic \
-device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \
-device cxl-rp,id=rp0,bus=cxl.0,chassis=0,port=0,slot=0 \
-object memory-backend-file,id=mem0,mem-path=/tmp/mem0,size=1G,share=true \
-device cxl-type3,bus=rp0,volatile-memdev=mem0,id=cxl-mem0 \
-M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G

[   13.936817] Call Trace:
[   13.970691]  <TASK>
[   13.990690]  device_add+0x39d/0x9a0
[   14.024690]  ? kobject_set_name_vargs+0x6d/0x90
[   14.066690]  ? dev_set_name+0x4b/0x60
[   14.090691]  devm_cxl_add_port+0x29a/0x4d0
[   14.135946]  cxl_acpi_probe+0xd9/0x2f0
[   14.167691]  ? device_pm_check_callbacks+0x36/0x100
[   14.203691]  platform_probe+0x44/0x90
[   14.247691]  really_probe+0xde/0x380
[   14.277690]  ? pm_runtime_barrier+0x50/0x90
[   14.324693]  __driver_probe_device+0x78/0x170
[   14.356694]  driver_probe_device+0x1f/0x90
[   14.396692]  __driver_attach+0xce/0x1c0
[   14.435691]  ? __pfx___driver_attach+0x10/0x10
[   14.471692]  bus_for_each_dev+0x73/0xa0
[   14.508693]  bus_add_driver+0x1ae/0x200
[   14.551691]  driver_register+0x89/0xe0
[   14.587691]  ? __pfx_cxl_acpi_init+0x10/0x10
[   14.625690]  do_one_initcall+0x59/0x230
[   14.814691]  kernel_init_freeable+0x204/0x24e
[   14.846710]  ? __pfx_kernel_init+0x10/0x10
[   14.899692]  kernel_init+0x16/0x140
[   14.954691]  ret_from_fork+0x2c/0x50
[   14.986692]  </TASK>
[   15.023689] Modules linked in:
[   15.057693] CR2: 0000000000000060
[   15.105691] ---[ end trace 0000000000000000 ]---
[   15.162837] RIP: 0010:bus_add_device+0x5b/0x150
[   15.217693] Code: 49 8b 74 24 20 48 89 df e8 92 88 ff ff 89 c5 85 c0 75 3b 48 8b 53 50 48 85 d2 75 03 48 8b 13 49 8b 84 24 a8 00 00 00 48 89 0
[   15.427859] RSP: 0000:ffffbd2a40013bc0 EFLAGS: 00010246
[   15.475692] RAX: 0000000000000000 RBX: ffff955c419e1800 RCX: 0000000000000000
[   15.591691] RDX: ffff955c41921778 RSI: ffff955c419e1800 RDI: ffff955c419e1800
[   15.703693] RBP: 0000000000000000 R08: 0000000000000228 R09: ffff955c4119e550
[   15.802711] R10: ffff955c414bedc8 R11: 0000000000000000 R12: ffffffff9e259d60
[   15.907692] R13: ffffffff9d3cee40 R14: ffff955c419e1800 R15: ffff955c41f06010
[   15.983693] FS:  0000000000000000(0000) GS:ffff955cbdd00000(0000) knlGS:0000000000000000
[   16.126698] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   16.206694] CR2: 0000000000000060 CR3: 0000000036010000 CR4: 00000000000006e0
[   16.347694] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009
[   16.348686] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]---