Re: [PATCH-SERIES qemu-server v3 0/4] cpu config: enable hv-evmcs for Windows 11/2022/2025 to mitigate issues with VBS

[Maximiliano Sandoval <m.sandoval@proxmox.com>]

Fiona Ebner <f.ebner@proxmox.com> writes:

> Changes in v3:
> * Improve commit message in patch 1.
> * Different approach, enable recommended hv-evmcs flag instead of
>   disabling apicv flags.
> * Mock host CPU vendor in tests.
>
> Changes in v2:
> * Disable MBEC by default for machine versions < 11.0 for backwards
>   compat with older kernel and QEMU.
>
> As reported in the community forum [0] and enterprise support, Windows
> with MBEC and VBS can have issues on certain Intel CPUs, leading to
> guest freezes and 100% CPU usage. The detection/enabling of APICv
> support in Windows was determined to be related. With hv_emcs, that
> feature is not used in Windows anymore. The flag is also recommended
> in the QEMU documentation [1], so start using it with a bumped
> 11.0+pve2 machine version.
>
> [0]: https://forum.proxmox.com/threads/184178
> [1]: https://www.qemu.org/docs/master/system/i386/hyperv.html#recommendations
>
> [..]

I tested this direction on my host with a AMD CPU as a smoke test and
updated the machine version from three Windows VMs from 10.1 to
11.0+pve2 (two were using i440fx and the third q35) from the web UI and
the VMs boot as expected. The windows versions were 2019, 2016, and
2022. I also tried with a Linux VM.

The code looks OK to me.

Tested-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
Reviewed-by: Maximiliano Sandoval <m.sandoval@proxmox.com>

-- 
Maximiliano