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arm64: Add HWCAP for self-synchronising virtual counter

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Since userspace can make use of the CNTVSS_EL0 instruction, expose
it via a HWCAP.

Suggested-by: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211017124225.3018098-18-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2021-10-17 13:42:25 +01:00 committed by Will Deacon
parent ae976f063b
commit fee29f008a
6 changed files with 19 additions and 3 deletions
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12
Documentation/arm64/cpu-feature-registers.rst
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@ -235,7 +235,15 @@ infrastructure:
| DPB | [3-0] | y |
+------------------------------+---------+---------+
6) ID_AA64MMFR2_EL1 - Memory model feature register 2
6) ID_AA64MMFR0_EL1 - Memory model feature register 0
+------------------------------+---------+---------+
| Name | bits | visible |
+------------------------------+---------+---------+
| ECV | [63-60] | y |
+------------------------------+---------+---------+
7) ID_AA64MMFR2_EL1 - Memory model feature register 2
+------------------------------+---------+---------+
| Name | bits | visible |
@ -243,7 +251,7 @@ infrastructure:
| AT | [35-32] | y |
+------------------------------+---------+---------+
7) ID_AA64ZFR0_EL1 - SVE feature ID register 0
8) ID_AA64ZFR0_EL1 - SVE feature ID register 0
+------------------------------+---------+---------+
| Name | bits | visible |

4
Documentation/arm64/elf_hwcaps.rst
View File

@ -247,6 +247,10 @@ HWCAP2_MTE
Functionality implied by ID_AA64PFR1_EL1.MTE == 0b0010, as described
by Documentation/arm64/memory-tagging-extension.rst.
HWCAP2_ECV
Functionality implied by ID_AA64MMFR0_EL1.ECV == 0b0001.
4. Unused AT_HWCAP bits
-----------------------

1
arch/arm64/include/asm/hwcap.h
View File

@ -105,6 +105,7 @@
#define KERNEL_HWCAP_RNG __khwcap2_feature(RNG)
#define KERNEL_HWCAP_BTI __khwcap2_feature(BTI)
#define KERNEL_HWCAP_MTE __khwcap2_feature(MTE)
#define KERNEL_HWCAP_ECV __khwcap2_feature(ECV)
/*
* This yields a mask that user programs can use to figure out what

1
arch/arm64/include/uapi/asm/hwcap.h
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@ -75,5 +75,6 @@
#define HWCAP2_RNG (1 << 16)
#define HWCAP2_BTI (1 << 17)
#define HWCAP2_MTE (1 << 18)
#define HWCAP2_ECV (1 << 19)
#endif /* _UAPI__ASM_HWCAP_H */

3
arch/arm64/kernel/cpufeature.c
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@ -279,7 +279,7 @@ static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64mmfr0[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_ECV_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_ECV_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_FGT_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR0_EXS_SHIFT, 4, 0),
/*
@ -2461,6 +2461,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
#ifdef CONFIG_ARM64_MTE
HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_MTE_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_MTE, CAP_HWCAP, KERNEL_HWCAP_MTE),
#endif /* CONFIG_ARM64_MTE */
HWCAP_CAP(SYS_ID_AA64MMFR0_EL1, ID_AA64MMFR0_ECV_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_ECV),
{},
};

1
arch/arm64/kernel/cpuinfo.c
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@ -94,6 +94,7 @@ static const char *const hwcap_str[] = {
[KERNEL_HWCAP_RNG] = "rng",
[KERNEL_HWCAP_BTI] = "bti",
[KERNEL_HWCAP_MTE] = "mte",
[KERNEL_HWCAP_ECV] = "ecv",
};
#ifdef CONFIG_COMPAT