linux-kernel - [PATCH] arm64: arm_pmuv3: Correctly extract and check the PMUVer

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Date: Mon, 8 Apr 2024 16:11:58 +0800
From: Yicong Yang <yangyicong@...wei.com>
To: <will@...nel.org>, <mark.rutland@....com>, <catalin.marinas@....com>,
	<broonie@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
CC: <jonathan.cameron@...wei.com>, <prime.zeng@...ilicon.com>,
	<linuxarm@...wei.com>, <yangyicong@...ilicon.com>
Subject: [PATCH] arm64: arm_pmuv3: Correctly extract and check the PMUVer

From: Yicong Yang <yangyicong@...ilicon.com>

Currently we're using "sbfx" to extract the PMUVer from ID_AA64DFR0_EL1
and skip the init/reset if no PMU present when the extracted PMUVer is
negative or is zero. However for PMUv3p8 the PMUVer will be 0b1000 and
PMUVer extracted by "sbfx" will always be negative and we'll skip the
init/reset in __init_el2_debug/reset_pmuserenr_el0 unexpectedly.

So this patch use "ubfx" instead of "sbfx" to extract the PMUVer. If
the PMUVer is implementation defined (0b1111) then reset it to zero
and skip the reset/init. Previously we'll also skip the init/reset
if the PMUVer is higher than the version we known (currently PMUv3p9),
with this patch we'll only skip if the PMU is not implemented or
implementation defined. This keeps consistence with how we probe
the PMU in the driver with pmuv3_implemented().

Signed-off-by: Yicong Yang <yangyicong@...ilicon.com>
---
 arch/arm64/include/asm/assembler.h | 5 ++++-
 arch/arm64/include/asm/el2_setup.h | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index ab8b396428da..3b7373d6c565 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -480,7 +480,10 @@ alternative_endif
  */
 	.macro	reset_pmuserenr_el0, tmpreg
 	mrs	\tmpreg, id_aa64dfr0_el1
-	sbfx	\tmpreg, \tmpreg, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
+	ubfx	\tmpreg, \tmpreg, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
+	cmp	\tmpreg, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF
+	csel	\tmpreg, xzr, \tmpreg, eq	// If PMU's IMP_DEF, regard it
+						// as not implemented and skip
 	cmp	\tmpreg, #1			// Skip if no PMU present
 	b.lt	9000f
 	msr	pmuserenr_el0, xzr		// Disable PMU access from EL0
diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
index b7afaa026842..2438e12b60c5 100644
--- a/arch/arm64/include/asm/el2_setup.h
+++ b/arch/arm64/include/asm/el2_setup.h
@@ -59,7 +59,10 @@
 
 .macro __init_el2_debug
 	mrs	x1, id_aa64dfr0_el1
-	sbfx	x0, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
+	ubfx	x0, x1, #ID_AA64DFR0_EL1_PMUVer_SHIFT, #4
+	cmp	x0, #ID_AA64DFR0_EL1_PMUVer_IMP_DEF
+	csel	x0, xzr, x0, eq			// If PMU's IMP_DEF, regard it
+						// as not implemented and skip
 	cmp	x0, #1
 	b.lt	.Lskip_pmu_\@			// Skip if no PMU present
 	mrs	x0, pmcr_el0			// Disable debug access traps
-- 
2.24.0