[PATCH 6.6.y] arm64: Filter out SVE hwcaps when FEAT_SVE isn't implemented

14 Feb 2025

commit 064737920bdbca86df91b96aed256e88018fef3a upstream.
The hwcaps code that exposes SVE features to userspace only
considers ID_AA64ZFR0_EL1, while this is only valid when
ID_AA64PFR0_EL1.SVE advertises that SVE is actually supported.
The expectations are that when ID_AA64PFR0_EL1.SVE is 0, the
ID_AA64ZFR0_EL1 register is also 0. So far, so good.
Things become a bit more interesting if the HW implements SME.
In this case, a few ID_AA64ZFR0_EL1 fields indicate *SME*
features. And these fields overlap with their SVE interpretations.
But the architecture says that the SME and SVE feature sets must
match, so we're still hunky-dory.
This goes wrong if the HW implements SME, but not SVE. In this
case, we end-up advertising some SVE features to userspace, even
if the HW has none. That's because we never consider whether SVE
is actually implemented. Oh well.
Fix it by restricting all SVE capabilities to ID_AA64PFR0_EL1.SVE
being non-zero. The HWCAPS documentation is amended to reflect the
actually checks performed by the kernel.
Fixes: 06a916feca2b ("arm64: Expose SVE2 features for userspace")
Reported-by: Catalin Marinas catalin.marinas@arm.com
Signed-off-by: Marc Zyngier maz@kernel.org
Signed-off-by: Mark Brown broonie@kernel.org
Cc: Will Deacon will@kernel.org
Cc: Mark Rutland mark.rutland@arm.com
Cc: stable@vger.kernel.org
Reviewed-by: Mark Brown broonie@kernel.org
Link: https://lore.kernel.org/r/20250107-arm64-2024-dpisa-v5-1-7578da51fc3d@kernel...
Signed-off-by: Will Deacon will@kernel.org
Signed-off-by: Marc Zyngier maz@kernel.org
---
 Documentation/arch/arm64/elf_hwcaps.rst | 36 +++++++++++++++--------
 arch/arm64/kernel/cpufeature.c          | 38 +++++++++++++++++--------
 2 files changed, 50 insertions(+), 24 deletions(-)

diff --git a/Documentation/arch/arm64/elf_hwcaps.rst b/Documentation/arch/arm64/elf_hwcaps.rst
index 76ff9d7398fda..f88a24d621dd4 100644
--- a/Documentation/arch/arm64/elf_hwcaps.rst
+++ b/Documentation/arch/arm64/elf_hwcaps.rst
@@ -174,22 +174,28 @@ HWCAP2_DCPODP
     Functionality implied by ID_AA64ISAR1_EL1.DPB == 0b0010.
HWCAP2_SVE2
-    Functionality implied by ID_AA64ZFR0_EL1.SVEVer == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.SVEver == 0b0001.
HWCAP2_SVEAES
-    Functionality implied by ID_AA64ZFR0_EL1.AES == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.AES == 0b0001.
HWCAP2_SVEPMULL
-    Functionality implied by ID_AA64ZFR0_EL1.AES == 0b0010.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.AES == 0b0010.
HWCAP2_SVEBITPERM
-    Functionality implied by ID_AA64ZFR0_EL1.BitPerm == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.BitPerm == 0b0001.
HWCAP2_SVESHA3
-    Functionality implied by ID_AA64ZFR0_EL1.SHA3 == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.SHA3 == 0b0001.
HWCAP2_SVESM4
-    Functionality implied by ID_AA64ZFR0_EL1.SM4 == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.SM4 == 0b0001.
HWCAP2_FLAGM2
     Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0010.
@@ -198,16 +204,20 @@ HWCAP2_FRINT
     Functionality implied by ID_AA64ISAR1_EL1.FRINTTS == 0b0001.
HWCAP2_SVEI8MM
-    Functionality implied by ID_AA64ZFR0_EL1.I8MM == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.I8MM == 0b0001.
HWCAP2_SVEF32MM
-    Functionality implied by ID_AA64ZFR0_EL1.F32MM == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.F32MM == 0b0001.
HWCAP2_SVEF64MM
-    Functionality implied by ID_AA64ZFR0_EL1.F64MM == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.F64MM == 0b0001.
HWCAP2_SVEBF16
-    Functionality implied by ID_AA64ZFR0_EL1.BF16 == 0b0001.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.BF16 == 0b0001.
HWCAP2_I8MM
     Functionality implied by ID_AA64ISAR1_EL1.I8MM == 0b0001.
@@ -273,7 +283,8 @@ HWCAP2_EBF16
     Functionality implied by ID_AA64ISAR1_EL1.BF16 == 0b0010.
HWCAP2_SVE_EBF16
-    Functionality implied by ID_AA64ZFR0_EL1.BF16 == 0b0010.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.BF16 == 0b0010.
HWCAP2_CSSC
     Functionality implied by ID_AA64ISAR2_EL1.CSSC == 0b0001.
@@ -282,7 +293,8 @@ HWCAP2_RPRFM
     Functionality implied by ID_AA64ISAR2_EL1.RPRFM == 0b0001.
HWCAP2_SVE2P1
-    Functionality implied by ID_AA64ZFR0_EL1.SVEver == 0b0010.
+    Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001 and
+    ID_AA64ZFR0_EL1.SVEver == 0b0010.
HWCAP2_SME2
     Functionality implied by ID_AA64SMFR0_EL1.SMEver == 0b0001.
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 7e96604559004..82778258855d1 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2762,6 +2762,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
    	.matches = match,						\
    }
+#define HWCAP_CAP_MATCH_ID(match, reg, field, min_value, cap_type, cap)		\
+	{									\
+		__HWCAP_CAP(#cap, cap_type, cap)				\
+		HWCAP_CPUID_MATCH(reg, field, min_value) 			\
+		.matches = match,						\
+	}
+
 #ifdef CONFIG_ARM64_PTR_AUTH
 static const struct arm64_cpu_capabilities ptr_auth_hwcap_addr_matches[] = {
    {
@@ -2790,6 +2797,13 @@ static const struct arm64_cpu_capabilities ptr_auth_hwcap_gen_matches[] = {
 };
 #endif
+#ifdef CONFIG_ARM64_SVE
+static bool has_sve_feature(const struct arm64_cpu_capabilities *cap, int scope)
+{
+	return system_supports_sve() && has_user_cpuid_feature(cap, scope);
+}
+#endif
+
 static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
    HWCAP_CAP(ID_AA64ISAR0_EL1, AES, PMULL, CAP_HWCAP, KERNEL_HWCAP_PMULL),
    HWCAP_CAP(ID_AA64ISAR0_EL1, AES, AES, CAP_HWCAP, KERNEL_HWCAP_AES),
@@ -2827,18 +2841,18 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
    HWCAP_CAP(ID_AA64MMFR2_EL1, AT, IMP, CAP_HWCAP, KERNEL_HWCAP_USCAT),
 #ifdef CONFIG_ARM64_SVE
    HWCAP_CAP(ID_AA64PFR0_EL1, SVE, IMP, CAP_HWCAP, KERNEL_HWCAP_SVE),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, SVEver, SVE2p1, CAP_HWCAP, KERNEL_HWCAP_SVE2P1),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, SVEver, SVE2, CAP_HWCAP, KERNEL_HWCAP_SVE2),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, AES, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEAES),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, AES, PMULL128, CAP_HWCAP, KERNEL_HWCAP_SVEPMULL),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, BitPerm, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEBITPERM),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, BF16, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEBF16),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, BF16, EBF16, CAP_HWCAP, KERNEL_HWCAP_SVE_EBF16),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, SHA3, IMP, CAP_HWCAP, KERNEL_HWCAP_SVESHA3),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, SM4, IMP, CAP_HWCAP, KERNEL_HWCAP_SVESM4),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, I8MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEI8MM),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, F32MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF32MM),
-	HWCAP_CAP(ID_AA64ZFR0_EL1, F64MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF64MM),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, SVEver, SVE2p1, CAP_HWCAP, KERNEL_HWCAP_SVE2P1),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, SVEver, SVE2, CAP_HWCAP, KERNEL_HWCAP_SVE2),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, AES, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEAES),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, AES, PMULL128, CAP_HWCAP, KERNEL_HWCAP_SVEPMULL),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, BitPerm, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEBITPERM),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, BF16, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEBF16),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, BF16, EBF16, CAP_HWCAP, KERNEL_HWCAP_SVE_EBF16),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, SHA3, IMP, CAP_HWCAP, KERNEL_HWCAP_SVESHA3),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, SM4, IMP, CAP_HWCAP, KERNEL_HWCAP_SVESM4),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, I8MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEI8MM),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, F32MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF32MM),
+	HWCAP_CAP_MATCH_ID(has_sve_feature, ID_AA64ZFR0_EL1, F64MM, IMP, CAP_HWCAP, KERNEL_HWCAP_SVEF64MM),
 #endif
    HWCAP_CAP(ID_AA64PFR1_EL1, SSBS, SSBS2, CAP_HWCAP, KERNEL_HWCAP_SSBS),
 #ifdef CONFIG_ARM64_BTI
-- 
2.39.2



    

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[PATCH 6.6.y] arm64: Filter out SVE hwcaps when FEAT_SVE isn't implemented