Change Details

It's not required, and causes the host to freeze when single-stepping a guest, for reasons that I don't understand. The problem appeared only after we started using VHE by default.

This is unneeded, and causes the host to freeze when VHE is enabled. In particular, when MDSCR_EL2.KDE is set to 1 and the CPU is executing at EL_D, i.e., EL2, debug exceptions are enabled. In non-VHE mode, we call into the guest by trapping to EL2, which implicitly masks debug exceptions by setting PSTATE.D. However, in VHE mode, PSTATE.D remains clear, so when the guest's MDSCR_EL1 value is loaded, we immediately begin single-stepping. In non-VHE mode there is no need to set KDE either, so just stop setting it.

It's not requiredThis is unneeded, and causes the host to freeze when single-stepping aVHE is enabled. guestIn particular, for reasons that I don't understand. The problem appeared onlywhen MDSCR_EL2.KDE is set to 1 and the CPU is executing after we started using VHE by default EL_D, i.e., EL2, debug exceptions are enabled. In non-VHE mode, we call into the guest by trapping to EL2, which implicitly masks debug exceptions by setting PSTATE.D. However, in VHE mode, PSTATE.D remains clear, so when the guest's MDSCR_EL1 value is loaded, we immediately begin single-stepping. In non-VHE mode there is no need to set KDE either, so just stop setting it.