[Bug 217400] New: Bugged RMRR prevents PCIe Passthrough of KVM VMs on certain platforms

[Bug 217400] New: Bugged RMRR prevents PCIe Passthrough of KVM VMs on certain platforms

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=217400

            Bug ID: 217400
           Summary: Bugged RMRR prevents PCIe Passthrough of KVM VMs on
                    certain platforms
           Product: Virtualization
           Version: unspecified
          Hardware: Intel
                OS: Linux
            Status: NEW
          Severity: high
          Priority: P3
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: bugtracker@fischbytes.de
        Regression: No

Certain vendors that are under the assumption that standards are for jerks and
Intel's specifications are a loose optional guideline have implemented RMRR in
such a way that every PCI device is marked as reserved and therefore cannot be
passed through to a virtual machine. This issue has been very well documented
by some people that have a lot more experience than I do at the below linked
resource. I was hoping that the upstream Linux kernel could implement the
Relaxed RMRR option, enabled by a kernel parameter at boot time, on these
bugged platforms as that would re-enable or rather enable a lot of broken
servers for the first time ever to use PCIe Passthrough. I can verify the issue
exists on a HPE DL360e Gen8 with trying to passthrough a GPU to a KVM/QEMU
machine. This bug is very much hardware specific, but seems to only exist on
Linux systems as they try to honor the Intel specifications as much as
possible, it was reported that other systems (e.g. VMWare ESXi) do not have
this issue as they ignore RMRR out-of-the-box. 

https://github.com/Aterfax/relax-intel-rmrr

I can confirm the patched Proxmox-Kernel works fine on an HPE DL360e Gen8. The
same bug was also reported to the openSUSE maintainers, they suggested to
report it here instead.

https://bugzilla.opensuse.org/show_bug.cgi?id=1211069

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