@gb.123 said in XCP-ng 8.3 updates announcements and testing:

Here is the summary:

If USB Keyboard & Mouse is passed-through along-with GPU:
The GPU gets stuck in D3 state (on Shutdown/Restart of VM) (Classic GPU reset problem)

If no vUSB is passed but GPU is passed through:
The GPU works correctly and resets correctly (on Shutdown/Restart of VM)

I have no clue what vUSB may change regarding GPU passthrough.

When I run :

$> lspci
Extract of Output (Partial):

07:00.0 USB controller: Advanced Micro Devices, Inc. [AMD] Device 15b8

However, this controller does not show up when I run :
xe pci-list

Is it a bug that lspci & xe pci-list have different number of devices ?

How can I pass this controller since xe pci-list does not show it so I can't get the UUID ?
Will kernel parameters (like XCP-ng 8.2) work in this case ?

Question for @Team-XAPI-Network regarding the filtering on PCI IDs.
I don't think XAPI allows using arbitrary BDF, but I may be wrong.

Is it safe to run on XCP-ng host ?

 echo 1 > /sys/bus/pci/rescan

(I'm trying to find a way where the PCI card is reset by the host without complete reboot, though I am aware that the above command will not reset it.)

Probably. But it's not going to change anything as the device doesn't completely leave the Dom0 when passed-through.
FYI a function-level-reset is systematically performed by Xen when doing PCI passthrough, thus your device should be reset before entering another guest (aside reset bugs like you may have).

Also is it advisable to use :

xl pci-assignable-add 07:00.0

in XCP-ng 8.3 ? or is this method deprecated ?

I don't think XAPI supports this PCI passthrough approach.
This is a command which allows dynamically to remove a device from Dom0 and put it into "quarantine domain", so that it will be ready to passthrough it.

Current XAPI uses the approach of having a set of "passthrough-able" devices at boot time by modifying the xen-pciback.hide kernel parameter, which does the same but at boot time.

Hello !

I am looking to get some feedback and evaluation on a performance-related patch for Xen (XCP-ng 8.3 only).
This patch changes the memcpy implementation of Xen to use the "ERMS variant" (aka REP MOVSB) instead of the current REP MOVSQ+B implementation.
This is expected to perform better on the vast majority of Intel CPUs and modern AMD ones (Zen3+), but may perform worse on some older AMD CPUs.

This change may impact the performance of PV drivers (especially network).

You can find more details regarding this proposed change in : https://github.com/xcp-ng-rpms/xen/pull/54
This change may be reworked in the future to take more in account the specificities of each CPUs (e.g check presence of ERMS flag).

Keep in mind that this patched version is experimental and not officially supported.

Installation :

# Download repo file for XCP-ng 8.3
wget https://koji.xcp-ng.org/repos/user/8/8.3/xcpng-users.repo -O /etc/yum.repos.d/xcpng-users.repo

# Installing the patched Xen packages (you should see `.erms` packages)
yum update --enablerepo=xcp-ng-tae1

You can revert the changes by downgrading the Xen package with the ones in the default repos.

yum downgrade --disablerepo=xcp-ng-tae1 "xen-*"

TSnake41 opened this pull request in xcp-ng-rpms/xen

draft Use ERMS variant for memcpy #54

@plaidypus I don't know a lot about NUMA on Xen, but we have a part in the docs regarding that
https://docs.xcp-ng.org/compute/#numa-affinity

And also other documentation on the subject
https://xapi-project.github.io/new-docs/toolstack/features/NUMA/index.html
there was a design session regarding NUMA in latest Xen Summit : https://youtu.be/KoNwEYMlhyU?list=PLQMQQsKgvLnvjRgDnb-5T51e1kGHgs1SO

@dcskinner @olivierlambert

You can read key/values from the xenstore, and write some (from VM to outside), but you cannot write values "in live" from outside the VM to the inside.

It is, but XAPI doesn't provide a interface for it.

do the guest tools quiesce the filesystems before snapshotting?

Tools are aware of a snapshot so you don't have blocks in flight.

do the guest tools quiesce the filesystems before snapshotting?

Guests kernel are aware, as it is them that are performing a "suspend" on toolstack request (thus quiece filesystems); although "tools" can only observe that the system has been suspended after the fact by measuring side effects, and not orchestrate it.

It's because suspend/resume operation doesn't come from "guest tools" actually, but instead from the kernel drivers. So userland tools has no say on it.

Hello,

Make sure Intel VMD is disabled (this is the hardware RAID feature of Intel, and it doesn't currently work on XCP-ng; you probably don't need it unless you are looking to make a RAID). We found some modern platforms enabling by default (which also causes issues with Windows).

@tuxen said (https://xcp-ng.org/forum/topic/3652/no-free-virtual-function-found-vgpu-s7150/4?_=1731502751059)

After some digging, could be the case of a GPU firmware being incompatible with UEFI. Do you have any spare server for testing XCP-ng boot in legacy/BIOS with this GPU?

Perhaps it is the issue ?

@ohajek

Nov 13 11:30:21 xen03 kernel: [10188.720655] AMD IOMMUv2 driver by Joerg Roedel jroedel@suse.de
Nov 13 11:30:21 xen03 kernel: [10188.720656] AMD IOMMUv2 functionality not available on this system

This is expected, Dom0 Kernel (Linux) is not supposed to access the IOMMU when it is already used by Xen. To check if AMD-Vi is working, you need to check xl dmesg instead.

I took a quick look at kern_gim_compiled.txt, and it look likes it timed-out somewhere

Oct 23 20:49:32 xen03 kernel: [   80.657394]        gim error:(wait_cmd_complete:2387)  wait_cmd_complete -- time out after 0.003004460 sec
Oct 23 20:49:32 xen03 kernel: [   80.657408]        gim error:(wait_cmd_complete:2390)   Cmd = 0x17, Status = 0x0, cmd_Complete=0

3ms looks like a short timeout for me, but aside that, it looks like a driver(gim) or hardware issue

@antest can you retry after doing /opt/xensource/libexec/xen-cmdline --set-xen iommu=debug then rebooting.
And also reporting full DomU and Dom0 dmesg (in addition to xl dmesg) ?

@abudef Note that even with this update, nested virtualization is still not really supported in XCP-ng 8.3.
It's there, you can enable it at your own risk. It broke due to some change in XAPI (even though Xen hypervisor had "support" for it).
It never actually got removed from Xen hypervisor (it was marked experimental in Xen 4.13 used in XCP-ng 8.2, it is also the case for Xen 4.17), although nothing really changed, it still has the same issues and limitations as said.

The current state of nested virtualization in Xen is quite clumsy and there are future plans to remake it properly from ground without taking shortcuts and have proper tests to back it.

Aside that, after some experiments, it seems that mostly nested EPT is incomplete/buggy, so your L1 hypervisor should not rely on it. You should add hap=0 to nested XCP-ng Xen cmdline. Beware that it will imply a pretty large performance hit, but I had more consistent results with this.
I am quite suprised that Windows works while Linux don't, maybe it is somewhat related to PV drivers ?

@hoh said in Early testable PVH support:

Then I tried to get rid of the (fake) UEFI magic.

Well, it is actually a full standard UEFI implementation, but that works in PVH instead of HVM.

I thought it should work to just change the PV-bootloader to pygrub. Calling pygrub on the disk image works fine and is able to extract the images and args

# pygrub -l alpine.img
Using <class 'grub.GrubConf.Grub2ConfigFile'> to parse /boot/grub/grub.cfg
title: Alpine, with Linux virt
  root: None
  kernel: /boot/vmlinuz-virt
  args: root=UUID=4c6dcb06-20ff-4bcf-be4d-cb399244c4c6 ro  rootfstype=ext4 console=hvc0
  initrd: /boot/initramfs-virt

But starting the VM fails. It looks like it starts but then immediately something calls force shutdown, I'll dive deeper into the logs later.

But setting everything manually actually works. If extract the kernel and initrd to dom-0 and configure

PV-kernel=/var/lib/xcp/guest/kernel
PV-ramdisk=/var/lib/xcp/guest/ramdisk
PV-args="root=/dev/xvda1 ro rootfstype=ext4 console=hvc0"

it boots and I looks pretty much the same as with the pvh-ovmf magic. So perhaps the idea to use pygrub is wrong.

I don't know how good is supported pygrub nowadays, especially since PV support got deprecated in XCP-ng 8.2 then completely dropped in XCP-ng 8.3; with the pv-shim (pv-in-pvh) being the only remaining (but not endorsed) way of booting some PV guests today.

In my tests, pygrub was very clunky and rarely work as I expect. In practice (what upstream Xen Project mostly uses), it got replaced with pvgrub/pvhgrub and pvh-ovmf (OvmfXen) which are more reliable and less problematic security-wise (runs in the guest rather than in the dom0).
(for using pvhgrub, you need to set a pvhgrub binary (grub-i386-xen_pvh.bin which is packaged by some distros like Alpine Linux's grub-xenhost) as kernel like done with pvh-ovmf)

@jbamford
Hello, can you give the output of xl info in Dom0 ? If you see hvm_directio in front of virt_caps, then PCI Passthrough is supported (i.e you have VT-d).

You can also check xl dmesg for vt-d specific messages (you can also give the output of it).

@EddieA Can you try differents combinations of passedthrough hardware in this VM ?

e.g try with each device one by one at a time; at least in the VM

@benapetr
Consider making a PR to https://github.com/xcp-ng/xcp-ng-org (https://github.com/xcp-ng/xcp-ng-org/blob/master/docs/management/management.md) if you want to make your project more visible.

@nvs can you try with a serial console and something listening on it; so when it crashes, we get the crash reason ?

@dcskinner @olivierlambert

You can read key/values from the xenstore, and write some (from VM to outside), but you cannot write values "in live" from outside the VM to the inside.

It is, but XAPI doesn't provide a interface for it.

do the guest tools quiesce the filesystems before snapshotting?

Tools are aware of a snapshot so you don't have blocks in flight.

do the guest tools quiesce the filesystems before snapshotting?

Guests kernel are aware, as it is them that are performing a "suspend" on toolstack request (thus quiece filesystems); although "tools" can only observe that the system has been suspended after the fact by measuring side effects, and not orchestrate it.

It's because suspend/resume operation doesn't come from "guest tools" actually, but instead from the kernel drivers. So userland tools has no say on it.

@antest can you try running the VM with only 1 vCPU ?

@antest can you retry after doing /opt/xensource/libexec/xen-cmdline --set-xen iommu=debug then rebooting.
And also reporting full DomU and Dom0 dmesg (in addition to xl dmesg) ?

Do you get anything special written to xl dmesg in Dom0 ?

@hitechhillbilly no it doesn't, it just ensures the N-th vCPU of Dom0 only runs on N-th pCPU of the machine.
Not sure about the practical impact of it, in the past it has been used for getting meaningful CPU temperatures from coretemp (with physical core matching virtual one), but that doesn't work anymore since Xen filters MSR accesses (including Dom0).

@dlucas said in XCP-NG 8.3 Crash on Shutdown - HP DL360 g9:

Have checked the IML log and the only thing that is being logged is this:

"13","Critical","PCI Bus","12/04/2025 00:03","12/04/2025 00:03","1","PCI Bus Error (Slot 0, Bus 0, Device 2, Function 2)",
"12","Critical","PCI Bus","12/03/2025 23:01","12/03/2025 23:01","1","PCI Bus Error (Slot 0, Bus 0, Device 2, Function 2)",
"11","Critical","PCI Bus","12/03/2025 22:53","12/03/2025 22:53","1","PCI Bus Error (Slot 0, Bus 0, Device 2, Function 2)",
"10","Critical","PCI Bus","12/01/2025 23:44","12/01/2025 23:44","1","PCI Bus Error (Slot 0, Bus 0, Device 2, Function 2)",
"9","Critical","PCI Bus","12/01/2025 01:31","12/01/2025 01:31","1","PCI Bus Error (Slot 0, Bus 0, Device 2, Function 2)",

I thought that a shutdown command from the command prompt solved the issue but it seems to always reboot when ever you tell it to shutdown.

What is device 00:02.2 (through lspci) ?