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Re: Xen panic due to xstate mismatch
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 5 Feb 2025 10:47:56 +0100
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>, Guillaume <thouveng@xxxxxxxxx>
- Delivery-date: Wed, 05 Feb 2025 09:48:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.02.2025 18:35, Andrew Cooper wrote:
> On 03/02/2025 8:58 am, Guillaume wrote:
>> Oh cool, thanks a lot for the explanation.
>> I added the "vzeroupper" and Xen crashes so it looks like the CPUID
>> emulation is buggy. Also I was able to try it using a VM (same debian
>> testing) running on virt-manager+kvm and it works fine (Xen in debug
>> mode). I will have a look by printing the xstate when running on
>> virt-manager+KVM and I will also run the xen-cpuid command to see the
>> difference just by curiosity as with your test we already spotted the
>> issue.
>> Thanks again for your enlightenment. I will continue my testing later
>> today and if you need me to test something else you are welcome, just
>> ask I will do my best.
>
> It sounds like KVM has a better CPUID emulation than VirtualBox.
>
> It would be ideal to report this bug with VirtualBox.
>
> But, as you identified originally, it's not nice that Xen simply like
> this. We should see about what to for Xen, seeing as we're close to the
> line on 4.20. I'm thinking maybe making the xstate checks non-fatal in
> the cpu_has_hypervisor case. Thoughts?
In principle: Yes, that's an option. But then we need to suppress use of
xstate_{,un}compressed_size() anywhere, perhaps by disabling respective
features. Not sure whether that is what you meant to imply.
Jan
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