Bug #15677
open
SVM should not blindly enable LBR-virt
0%
Description
The logic for initializing the VMCB under bhyve is blindly enabling the LBR virtualization feature without first checking for it in the appropriate CPUID leaf. This has been working by chance, since all modern CPUs appear to support this feature.
Furthermore, the VMCB initialization routine should not be enabling LBR for the guest (by setting bit 0 in vmcb`dbgctl) If the guest wants that functionality, they can choose to enable it themself.
Related issues
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Updated by Patrick Mooney 12 days ago
With the proposed fix for this change running on AMD gear, I checked that LBR-virt was being enabled by default (it's part of the required feature set for now). With the corresponding feature in svm_feature manually masked out via mdb-kw, I confirmed that the LBR-virt bit in the misc_ctrl field of the VMCB was absent.
Updated by Patrick Mooney 12 days ago
- Related to Bug #15676: SVM feature detection broken in bhyve added