linux-kernel - [PATCH AUTOSEL 5.5 350/542] arm64: cpufeature: Set the FP/SIMD compat HWCAP bits properly

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Message-Id: <20200214154854.6746-350-sashal@kernel.org>
Date:   Fri, 14 Feb 2020 10:45:42 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Sasha Levin <sashal@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 5.5 350/542] arm64: cpufeature: Set the FP/SIMD compat HWCAP bits properly

From: Suzuki K Poulose <suzuki.poulose@....com>

[ Upstream commit 7559950aef1ab8792c50797c6c5c7c5150a02460 ]

We set the compat_elf_hwcap bits unconditionally on arm64 to
include the VFP and NEON support. However, the FP/SIMD unit
is optional on Arm v8 and thus could be missing. We already
handle this properly in the kernel, but still advertise to
the COMPAT applications that the VFP is available. Fix this
to make sure we only advertise when we really have them.

Fixes: 82e0191a1aa11abf ("arm64: Support systems without FP/ASIMD")
Cc: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/kernel/cpufeature.c | 37 +++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b4f84513655d6..32eff833a43c5 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -32,9 +32,7 @@ static unsigned long elf_hwcap __read_mostly;
 #define COMPAT_ELF_HWCAP_DEFAULT	\
 				(COMPAT_HWCAP_HALF|COMPAT_HWCAP_THUMB|\
 				 COMPAT_HWCAP_FAST_MULT|COMPAT_HWCAP_EDSP|\
-				 COMPAT_HWCAP_TLS|COMPAT_HWCAP_VFP|\
-				 COMPAT_HWCAP_VFPv3|COMPAT_HWCAP_VFPv4|\
-				 COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV|\
+				 COMPAT_HWCAP_TLS|COMPAT_HWCAP_IDIV|\
 				 COMPAT_HWCAP_LPAE)
 unsigned int compat_elf_hwcap __read_mostly = COMPAT_ELF_HWCAP_DEFAULT;
 unsigned int compat_elf_hwcap2 __read_mostly;
@@ -1596,6 +1594,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.match_list = list,						\
 	}
 
+#define HWCAP_CAP_MATCH(match, cap_type, cap)					\
+	{									\
+		__HWCAP_CAP(#cap, cap_type, cap)				\
+		.matches = match,						\
+	}
+
 #ifdef CONFIG_ARM64_PTR_AUTH
 static const struct arm64_cpu_capabilities ptr_auth_hwcap_addr_matches[] = {
 	{
@@ -1669,8 +1673,35 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	{},
 };
 
+#ifdef CONFIG_COMPAT
+static bool compat_has_neon(const struct arm64_cpu_capabilities *cap, int scope)
+{
+	/*
+	 * Check that all of MVFR1_EL1.{SIMDSP, SIMDInt, SIMDLS} are available,
+	 * in line with that of arm32 as in vfp_init(). We make sure that the
+	 * check is future proof, by making sure value is non-zero.
+	 */
+	u32 mvfr1;
+
+	WARN_ON(scope == SCOPE_LOCAL_CPU && preemptible());
+	if (scope == SCOPE_SYSTEM)
+		mvfr1 = read_sanitised_ftr_reg(SYS_MVFR1_EL1);
+	else
+		mvfr1 = read_sysreg_s(SYS_MVFR1_EL1);
+
+	return cpuid_feature_extract_unsigned_field(mvfr1, MVFR1_SIMDSP_SHIFT) &&
+		cpuid_feature_extract_unsigned_field(mvfr1, MVFR1_SIMDINT_SHIFT) &&
+		cpuid_feature_extract_unsigned_field(mvfr1, MVFR1_SIMDLS_SHIFT);
+}
+#endif
+
 static const struct arm64_cpu_capabilities compat_elf_hwcaps[] = {
 #ifdef CONFIG_COMPAT
+	HWCAP_CAP_MATCH(compat_has_neon, CAP_COMPAT_HWCAP, COMPAT_HWCAP_NEON),
+	HWCAP_CAP(SYS_MVFR1_EL1, MVFR1_SIMDFMAC_SHIFT, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP, COMPAT_HWCAP_VFPv4),
+	/* Arm v8 mandates MVFR0.FPDP == {0, 2}. So, piggy back on this for the presence of VFP support */
+	HWCAP_CAP(SYS_MVFR0_EL1, MVFR0_FPDP_SHIFT, FTR_UNSIGNED, 2, CAP_COMPAT_HWCAP, COMPAT_HWCAP_VFP),
+	HWCAP_CAP(SYS_MVFR0_EL1, MVFR0_FPDP_SHIFT, FTR_UNSIGNED, 2, CAP_COMPAT_HWCAP, COMPAT_HWCAP_VFPv3),
 	HWCAP_CAP(SYS_ID_ISAR5_EL1, ID_ISAR5_AES_SHIFT, FTR_UNSIGNED, 2, CAP_COMPAT_HWCAP2, COMPAT_HWCAP2_PMULL),
 	HWCAP_CAP(SYS_ID_ISAR5_EL1, ID_ISAR5_AES_SHIFT, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP2, COMPAT_HWCAP2_AES),
 	HWCAP_CAP(SYS_ID_ISAR5_EL1, ID_ISAR5_SHA1_SHIFT, FTR_UNSIGNED, 1, CAP_COMPAT_HWCAP2, COMPAT_HWCAP2_SHA1),
-- 
2.20.1