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

Message ID 20241203193220.1070811-13-oliver.upton@linux.dev (mailing list archive)
State New
Headers show
Series KVM: arm64: Support FEAT_PMUv3 on Apple hardware | expand

Commit Message

Oliver Upton Dec. 3, 2024, 7:32 p.m. UTC 
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(-)
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Patch

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;