From c5c0632b9c7b80914f8704b10e2ebd4adf41ed2a Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 14 Feb 2018 17:21:57 +0000 Subject: [PATCH] arm64: perf: correct PMUVer probing [ Upstream commit 0331365edb1d6ccd6ae68b1038111da85d4c68d1 ] The ID_AA64DFR0_EL1.PMUVer field doesn't follow the usual ID registers scheme. While value 0xf indicates a non-architected PMU is implemented, values 0x1 to 0xe indicate an increasingly featureful architected PMU, as if the field were unsigned. For more details, see ARM DDI 0487C.a, D10.1.4, "Alternative ID scheme used for the Performance Monitors Extension version". Currently, we treat the field as signed, and erroneously bail out for values 0x8 to 0xe. Let's correct that. Signed-off-by: Mark Rutland Reviewed-by: Robin Murphy Cc: Will Deacon Signed-off-by: Will Deacon Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/perf_event.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index 9eaef51..1984e73 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -914,9 +914,9 @@ static void __armv8pmu_probe_pmu(void *info) int pmuver; dfr0 = read_sysreg(id_aa64dfr0_el1); - pmuver = cpuid_feature_extract_signed_field(dfr0, + pmuver = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_PMUVER_SHIFT); - if (pmuver < 1) + if (pmuver == 0xf || pmuver == 0) return; probe->present = true; -- 2.7.4