From: Alexandru Elisei alexandru.elisei@arm.com
[ Upstream commit 506506cad3947b942425b119ffa2b06715d5d804 ]
Commit b20d1ba3cf4b ("arm64: cpufeature: allow for version discrepancy in PMU implementations") made it possible to run Linux on a machine with PMUs with different versions without tainting the kernel. The patch relaxed the restriction only for the ID_AA64DFR0_EL1.PMUVer field, and missed doing the same for ID_DFR0_EL1.PerfMon , which also reports the PMU version, but for the AArch32 state.
For example, with Linux running on two clusters with different PMU versions, the kernel is tainted when bringing up secondaries with the following message:
[ 0.097027] smp: Bringing up secondary CPUs ... [..] [ 0.142805] Detected PIPT I-cache on CPU4 [ 0.142805] CPU features: SANITY CHECK: Unexpected variation in SYS_ID_DFR0_EL1. Boot CPU: 0x00000004011088, CPU4: 0x00000005011088 [ 0.143555] CPU features: Unsupported CPU feature variation detected. [ 0.143702] GICv3: CPU4: found redistributor 10000 region 0:0x000000002f180000 [ 0.143702] GICv3: CPU4: using allocated LPI pending table @0x00000008800d0000 [ 0.144888] CPU4: Booted secondary processor 0x0000010000 [0x410fd0f0]
The boot CPU implements FEAT_PMUv3p1 (ID_DFR0_EL1.PerfMon, bits 27:24, is 0b0100), but CPU4, part of the other cluster, implements FEAT_PMUv3p4 (ID_DFR0_EL1.PerfMon = 0b0101).
Treat the PerfMon field as FTR_NONSTRICT and FTR_EXACT to pass the sanity check and to match how PMUVer is treated for the 64bit ID register.
Fixes: b20d1ba3cf4b ("arm64: cpufeature: allow for version discrepancy in PMU implementations") Signed-off-by: Alexandru Elisei alexandru.elisei@arm.com Link: https://lore.kernel.org/r/20220617111332.203061-1-alexandru.elisei@arm.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/cpufeature.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 5357ba7ea3c7..a54f34aa36e0 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -541,7 +541,7 @@ static const struct arm64_ftr_bits ftr_id_pfr2[] = {
static const struct arm64_ftr_bits ftr_id_dfr0[] = { /* [31:28] TraceFilt */ - S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR0_PERFMON_SHIFT, 4, 0xf), + S_ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_EXACT, ID_DFR0_PERFMON_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR0_MPROFDBG_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR0_MMAPTRC_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_DFR0_COPTRC_SHIFT, 4, 0),