microsoft / microsoft/openvmm

openhcl/vmbus_relay: posting sint messages fails when guest enables/disables simp

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@SvenGroot is already working on this.

Since Oct 27, 2025.

bug enhancement
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Rust
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Description

With certain vmbus clients like the crash vmbus client in windows that enable and disable the simp, it seems that openhcl will attempt to call post_message on the hypervisor with the simp disabled, which the hypervisor will fail.

Unclear if we should queue the message or do something else. See https://openvmm.dev/test-results/test.html?run=18654373886&job=x64-windows-intel-tdx-vmm-tests-logs&test=multiarch__vmbus_relay__hyperv_openhcl_uefi_x64_windows_datacenter_core_2025_x64_prepped_tdx_vmbus_relay_force_mnf# where we are in a bugcheck path, and we attempt to post messages with the simp disabled.

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