CONFIG_KVM_BOOK3S_HV_NESTED_PMU_WORKAROUND: Nested L0 host workaround for L1 KVM host PMU handling bug

General informations

The Linux kernel configuration item CONFIG_KVM_BOOK3S_HV_NESTED_PMU_WORKAROUND:

• prompt: Nested L0 host workaround for L1 KVM host PMU handling bug
• type: bool
• depends on: ( CONFIG_EXPERT ) && ( CONFIG_KVM_BOOK3S_HV_POSSIBLE )
• defined in arch/powerpc/kvm/Kconfig
• found in Linux kernels: 5.17–5.19, 6.0–6.8, 6.9-rc+HEAD

Help text

Old nested HV capable Linux guests have a bug where they don't reflect the PMU in-use status of their L2 guest to the L0 host while the L2 PMU registers are live. This can result in loss of L2 PMU register state, causing perf to not work correctly in L2 guests.

Selecting this option for the L0 host implements a workaround for those buggy L1s which saves the L2 state, at the cost of performance in all nested-capable guest entry/exit.

Hardware

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Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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