[RFC PATCH 12/14] KVM: arm64: Advertise PMUv3 if IMPDEF traps are present

[Oliver Upton <oliver.upton@linux.dev>]

Advertise a baseline PMUv3 implementation when running on hardware with
IMPDEF traps of the PMUv3 sysregs.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/pmu-emul.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 8a565817a814..34d9c08af209 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -1260,7 +1260,17 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)
 	pmuver = SYS_FIELD_GET(ID_AA64DFR0_EL1, PMUVer,
 			       read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1));
 
-	/* Treat IMPLEMENTATION DEFINED functionality as unimplemented */
+	/*
+	 * Spoof a barebones PMUv3 implementation if the system supports IMPDEF
+	 * traps of the PMUv3 sysregs
+	 */
+	if (cpus_have_final_cap(ARM64_WORKAROUND_PMUV3_IMPDEF_TRAPS))
+		return ID_AA64DFR0_EL1_PMUVer_IMP;
+
+	/*
+	 * Otherwise, treat IMPLEMENTATION DEFINED functionality as
+	 * unimplemented
+	 */
 	if (pmuver == ID_AA64DFR0_EL1_PMUVer_IMP_DEF)
 		return 0;
 
-- 
2.39.5