linux-kernel - [PATCH 5.11 083/342] kselftest/arm64: mte: Fix MTE feature detection

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Date:   Mon, 10 May 2021 12:17:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andre Przywara <andre.przywara@....com>,
        Mark Brown <broonie@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 083/342] kselftest/arm64: mte: Fix MTE feature detection

From: Andre Przywara <andre.przywara@....com>

[ Upstream commit 592432862cc4019075a7196d9961562c49507d6f ]

To check whether the CPU and kernel support the MTE features we want
to test, we use an (emulated) CPU ID register read. However we only
check against a very particular feature version (0b0010), even though
the ARM ARM promises ID register features to be backwards compatible.

While this could be fixed by using ">=" instead of "==", we should
actually use the explicit HWCAP2_MTE hardware capability, exposed by the
kernel via the ELF auxiliary vectors.

That moves this responsibility to the kernel, and fixes running the
tests on machines with FEAT_MTE3 capability.

Signed-off-by: Andre Przywara <andre.przywara@....com>
Reviewed-by: Mark Brown <broone@...nel.org>
Link: https://lore.kernel.org/r/20210319165334.29213-7-andre.przywara@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/testing/selftests/arm64/mte/mte_common_util.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/arm64/mte/mte_common_util.c b/tools/testing/selftests/arm64/mte/mte_common_util.c
index 39f8908988ea..70665ba88cbb 100644
--- a/tools/testing/selftests/arm64/mte/mte_common_util.c
+++ b/tools/testing/selftests/arm64/mte/mte_common_util.c
@@ -278,22 +278,13 @@ int mte_switch_mode(int mte_option, unsigned long incl_mask)
 	return 0;
 }
 
-#define ID_AA64PFR1_MTE_SHIFT		8
-#define ID_AA64PFR1_MTE			2
-
 int mte_default_setup(void)
 {
-	unsigned long hwcaps = getauxval(AT_HWCAP);
+	unsigned long hwcaps2 = getauxval(AT_HWCAP2);
 	unsigned long en = 0;
 	int ret;
 
-	if (!(hwcaps & HWCAP_CPUID)) {
-		ksft_print_msg("FAIL: CPUID registers unavailable\n");
-		return KSFT_FAIL;
-	}
-	/* Read ID_AA64PFR1_EL1 register */
-	asm volatile("mrs %0, id_aa64pfr1_el1" : "=r"(hwcaps) : : "memory");
-	if (((hwcaps >> ID_AA64PFR1_MTE_SHIFT) & MT_TAG_MASK) != ID_AA64PFR1_MTE) {
+	if (!(hwcaps2 & HWCAP2_MTE)) {
 		ksft_print_msg("FAIL: MTE features unavailable\n");
 		return KSFT_SKIP;
 	}
-- 
2.30.2