[Bug 219009] Random host reboots on Ryzen 7000/8000 using nested VMs (vls suspected)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=219009

--- Comment #23 from mlevitsk@redhat.com ---
On Sat, 2024-07-06 at 11:20 +0000, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=219009
> 
>             Bug ID: 219009
>            Summary: Random host reboots on Ryzen 7000/8000 using nested
>                     VMs (vls suspected)
>            Product: Virtualization
>            Version: unspecified
>           Hardware: AMD
>                 OS: Linux
>             Status: NEW
>           Severity: high
>           Priority: P3
>          Component: kvm
>           Assignee: virtualization_kvm@kernel-bugs.osdl.org
>           Reporter: zaltys@natrix.lt
>         Regression: No
> 
> Running nested VMs on AMD Ryzen 7000/8000 (ZEN4) CPUs results in random
> host's
> reboots.
> 
> There is no kernel panic, no log entries, no relevant output to serial
> console.
> It is as if platform is simply hard reset. It seems time to reproduce it
> varies
> from system to system and can be dependent on workload and even specific CPU
> model.
> 
> I can reproduce it with kernel 6.9.7 and qemu 9.0 on Ryzen 7950X3D under one
> hour by using KVM -> Windows 10/11 with Hyper-V services on or KVM -> Windows
> 10/11 with 3 VBox VMs (also Win11) running. Others people had it repeatedly
> reproduced on Ryzen 7700,7600 and 8700GE, including KVM -> KVM -> Linux.[1] I
> also have seen Hetzner (company offering Ryzen based dedicated servers)
> customers complaining about similiar random reboots.
> 
> I tried looking up errata for Ryzen 7000/8000, but could not find one
> published, so I decided to check errata for EPYC 9004 [2], which is also Zen4
> arch as Ryzen 7000/8000. It has nesting related bug #1495 (on page 49), which
> mentions using Virtualized VMLOAD/VMSAVE can result in MCE and/or system
> reset. 
> 
> Based on that errata mentioned above, I reconfigured my system with
> kvm_amd.vls=0 and for me random reboots with nested virtualization stopped.
> Same was reported by several people from [1].
> 
> Somebody from AMD must be asked to confirm if it is really Ryzen 7000/8000
> hardware bug, and if there is a better fix than disabling VLS as it has
> performance hit. If disabling it is the only fix, then kvm_amd.vls=0 must be
> default for Ryzen 7000/8000.
> 
> [1]
>
> https://www.reddit.com/r/Proxmox/comments/1cym3pl/nested_virtualization_crashing_ryzen_7000_series/
> [2]
>
> https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/revision-guides/57095-PUB_1_01.pdf
> 

Hi!

Can someone from AMD take a look at this bug:

From the bug report it appears that recent Zen4 CPUs have errata in their
virtual VMLOAD/VMSAVE implemenatation,
which causes random host reboots (#MC?) when nesting is used, which is IMHO a
quite serious issue.


Thanks,
Best regards,
       Maxim Levitsky

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