[PATCH 0/4] KVM: arm64: PMU: Fix PMUVer handling on heterogeneous PMU systems

[Reiji Watanabe]

This series fixes issues with PMUVer handling for a guest with
PMU configured on heterogeneous PMU systems.
Specifically, it addresses the following two issues.

[A] The default value of ID_AA64DFR0_EL1.PMUVer of the vCPU is set
    to its sanitized value.  This could be inappropriate on
    heterogeneous PMU systems, as arm64_ftr_bits for PMUVer is defined
    as FTR_EXACT with safe_val == 0 (when ID_AA64DFR0_EL1.PMUVer of all
    PEs on the host is not uniform, the sanitized value will be 0).

[B] KVM uses PMUVer of the PMU hardware that is associated to
    the guest (kvm->arch.arm_pmu->pmuver) for the guest in some
    cases, even though userspace might have changed the guest's
    ID_AA64DFR0_EL1.PMUVer (kvm->arch.dfr0_pmuver.imp).

To fix [A], KVM will set the default value of the guest's
ID_AA64DFR0_EL1.PMUVer to the PMUVer of the guest's PMU
(kvm->arch.arm_pmu->pmuver).

To fix [B], KVM will stop using kvm->arch.arm_pmu->pmuver (except
for some special cases) and use ID_AA64DFR0_EL1.PMUVer for the
guest instead.

Patch 1 adds a helper to set a PMU for the guest. This helper will
make it easier for the following patches to modify the relevant
code.

Patch 2 make the default PMU for the guest set on the first
vCPU reset. As userspace can get the value of ID_AA64DFR0_EL1
after the initial vCPU reset, this change is to make the
default PMUVer value based on the guest's PMU available on
the initial vCPU reset.

Patch 3 and 4 fix the issue [A] and [B] respectively.

The series is based on v6.4-rc3.
The patches in this series were originally included as part of [1].

[1] https://lore.kernel.org/all/20230211031506.4159098-1-reijiw@google.com/

Reiji Watanabe (4):
  KVM: arm64: PMU: Introduce a helper to set the guest's PMU
  KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset
  KVM: arm64: PMU: Use PMUVer of the guest's PMU for ID_AA64DFR0.PMUVer
  KVM: arm64: PMU: Don't use the PMUVer of the PMU set for guest

 arch/arm64/include/asm/kvm_host.h |  2 +
 arch/arm64/kvm/arm.c              |  6 ---
 arch/arm64/kvm/pmu-emul.c         | 73 +++++++++++++++++++++----------
 arch/arm64/kvm/reset.c            | 20 ++++++---
 arch/arm64/kvm/sys_regs.c         | 48 +++++++++++++-------
 include/kvm/arm_pmu.h             | 10 ++++-
 6 files changed, 106 insertions(+), 53 deletions(-)


base-commit: 44c026a73be8038f03dbdeef028b642880cf1511
-- 
2.41.0.rc0.172.g3f132b7071-goog