Re: [PATCH 2/2] arm64: Expose Arm v8.4 features

From: Suzuki K Poulose
Date: Wed Feb 07 2018 - 05:52:03 EST

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On 07/02/18 10:43, Dave Martin wrote:

On Thu, Feb 01, 2018 at 10:38:38AM +0000, Suzuki K Poulose wrote:

Expose the new features introduced by Arm v8.4 extensions to
Arm v8-A profile.

These include :

1) Data indpendent timing of instructions. (DIT, exposed as HWCAP_DIT)
2) Unaligned atomic instructions and Single-copy atomicity of loads
and stores. (AT, expose as HWCAP_USCAT)
3) LDAPR and STLR instructions with immediate offsets (extension to
LRCPC, exposed as HWCAP_ILRCPC)
4) Flag manipulation instructions (TS, exposed as HWCAP_FLAGM).

While at it get rid of the RES0 entries in the cpu-feature-registers.txt
documentation.

Should we write somewhere than fields that are not described here are
implicitly RES0, or would that be too strong a statement?

Dave,

We already have the following description in the file :

"The following rules are applied to the value returned by the
infrastructure:

a) The value of an 'IMPLEMENTATION DEFINED' field is set to 0.
b) The value of a reserved field is populated with the reserved
value as defined by the architecture.
c) The value of a 'visible' field holds the system wide safe value
for the particular feature (except for MIDR_EL1, see section 4).
d) All other fields (i.e, invisible fields) are set to indicate
the feature is missing (as defined by the architecture).
"

So we don't have to bother if the fields are RES0 or they get
some definitions in the future, as long as we don't expose them.

Cheers
Suzuki

Cheers
---Dave

Cc: Dave Martin <dave.martin@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
Documentation/arm64/cpu-feature-registers.txt | 18 ++++++++++--------
Documentation/arm64/elf_hwcaps.txt | 16 ++++++++++++++++
arch/arm64/include/asm/sysreg.h | 3 +++
arch/arm64/include/uapi/asm/hwcap.h | 4 ++++
arch/arm64/kernel/cpufeature.c | 7 +++++++
arch/arm64/kernel/cpuinfo.c | 4 ++++
6 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/Documentation/arm64/cpu-feature-registers.txt b/Documentation/arm64/cpu-feature-registers.txt
index a70090b28b07..7964f03846b1 100644
--- a/Documentation/arm64/cpu-feature-registers.txt
+++ b/Documentation/arm64/cpu-feature-registers.txt
@@ -110,7 +110,7 @@ infrastructure:
x--------------------------------------------------x
| Name | bits | visible |
|--------------------------------------------------|
- | RES0 | [63-52] | n |
+ | TS | [55-52] | y |
|--------------------------------------------------|
| FHM | [51-48] | y |
|--------------------------------------------------|
@@ -124,8 +124,6 @@ infrastructure:
|--------------------------------------------------|
| RDM | [31-28] | y |
|--------------------------------------------------|
- | RES0 | [27-24] | n |
- |--------------------------------------------------|
| ATOMICS | [23-20] | y |
|--------------------------------------------------|
| CRC32 | [19-16] | y |
@@ -135,8 +133,6 @@ infrastructure:
| SHA1 | [11-8] | y |
|--------------------------------------------------|
| AES | [7-4] | y |
- |--------------------------------------------------|
- | RES0 | [3-0] | n |
x--------------------------------------------------x
@@ -144,12 +140,10 @@ infrastructure:
x--------------------------------------------------x
| Name | bits | visible |
|--------------------------------------------------|
- | RES0 | [63-36] | n |
+ | DIT | [51-48] | y |
|--------------------------------------------------|
| SVE | [35-32] | y |
|--------------------------------------------------|
- | RES0 | [31-28] | n |
- |--------------------------------------------------|
| GIC | [27-24] | n |
|--------------------------------------------------|
| AdvSIMD | [23-20] | y |
@@ -199,6 +193,14 @@ infrastructure:
| DPB | [3-0] | y |
x--------------------------------------------------x
+ 5) ID_AA64MMFR2_EL1 - Memory model feature register 2
+
+ x--------------------------------------------------x
+ | Name | bits | visible |
+ |--------------------------------------------------|
+ | AT | [35-32] | y |
+ x--------------------------------------------------x
+
Appendix I: Example
---------------------------
diff --git a/Documentation/arm64/elf_hwcaps.txt b/Documentation/arm64/elf_hwcaps.txt
index 57324ee55ecc..d6aff2c5e9e2 100644
--- a/Documentation/arm64/elf_hwcaps.txt
+++ b/Documentation/arm64/elf_hwcaps.txt
@@ -162,3 +162,19 @@ HWCAP_SVE
HWCAP_ASIMDFHM
Functionality implied by ID_AA64ISAR0_EL1.FHM == 0b0001.
+
+HWCAP_DIT
+
+ Functionality implied by ID_AA64PFR0_EL1.DIT == 0b0001.
+
+HWCAP_USCAT
+
+ Functionality implied by ID_AA64MMFR2_EL1.AT == 0b0001.
+
+HWCAP_ILRCPC
+
+ Functionality implied by ID_AA64ISR1_EL1.LRCPC == 0b0002.
+
+HWCAP_FLAGM
+
+ Functionality implied by ID_AA64ISAR0_EL1.TS == 0b0001.
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 0e1960c59197..e7b9f154e476 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -490,6 +490,7 @@
#define SCTLR_EL1_BUILD_BUG_ON_MISSING_BITS BUILD_BUG_ON((SCTLR_EL1_SET ^ SCTLR_EL1_CLEAR) != ~0)
/* id_aa64isar0 */
+#define ID_AA64ISAR0_TS_SHIFT 52
#define ID_AA64ISAR0_FHM_SHIFT 48
#define ID_AA64ISAR0_DP_SHIFT 44
#define ID_AA64ISAR0_SM4_SHIFT 40
@@ -511,6 +512,7 @@
/* id_aa64pfr0 */
#define ID_AA64PFR0_CSV3_SHIFT 60
#define ID_AA64PFR0_CSV2_SHIFT 56
+#define ID_AA64PFR0_DIT_SHIFT 48
#define ID_AA64PFR0_SVE_SHIFT 32
#define ID_AA64PFR0_RAS_SHIFT 28
#define ID_AA64PFR0_GIC_SHIFT 24
@@ -568,6 +570,7 @@
#define ID_AA64MMFR1_VMIDBITS_16 2
/* id_aa64mmfr2 */
+#define ID_AA64MMFR2_AT_SHIFT 32
#define ID_AA64MMFR2_LVA_SHIFT 16
#define ID_AA64MMFR2_IESB_SHIFT 12
#define ID_AA64MMFR2_LSM_SHIFT 8
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index f018c3deea3b..17c65c8f33cb 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -44,5 +44,9 @@
#define HWCAP_SHA512 (1 << 21)
#define HWCAP_SVE (1 << 22)
#define HWCAP_ASIMDFHM (1 << 23)
+#define HWCAP_DIT (1 << 24)
+#define HWCAP_USCAT (1 << 25)
+#define HWCAP_ILRCPC (1 << 26)
+#define HWCAP_FLAGM (1 << 27)
#endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 1c39a635a71c..796e83dde9fc 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -123,6 +123,7 @@ cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
* sync with the documentation of the CPU feature register ABI.
*/
static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
+ ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_TS_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_FHM_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_DP_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_SM4_SHIFT, 4, 0),
@@ -148,6 +149,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV2_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_DIT_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_RAS_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_GIC_SHIFT, 4, 0),
@@ -192,6 +194,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr1[] = {
};
static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = {
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_AT_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_LVA_SHIFT, 4, 0),
/* While IESB is good to have, it is not fatal if we miss this on some CPUs */
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR2_IESB_SHIFT, 4, 0),
@@ -1083,14 +1086,18 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_SM4_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_SM4),
HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_DP_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_ASIMDDP),
HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_FHM_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_ASIMDFHM),
+ HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_TS_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FLAGM),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, HWCAP_FP),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_FPHP),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, HWCAP_ASIMD),
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_ASIMDHP),
+ HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_DIT_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_DIT),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_DPB_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_DCPOP),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_JSCVT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_JSCVT),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FCMA_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_FCMA),
HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_LRCPC),
+ HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 2, CAP_HWCAP, HWCAP_ILRCPC),
+ HWCAP_CAP(SYS_ID_AA64MMFR2_EL1, ID_AA64MMFR2_AT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_USCAT),
#ifdef CONFIG_ARM64_SVE
HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_SVE_SHIFT, FTR_UNSIGNED, ID_AA64PFR0_SVE, CAP_HWCAP, HWCAP_SVE),
#endif
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 7f94623df8a5..e9ab7b3ed317 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -77,6 +77,10 @@ static const char *const hwcap_str[] = {
"sha512",
"sve",
"asimdfhm",
+ "dit",
+ "uscat",
+ "ilrcpc",
+ "flagm",
NULL
};
--
2.14.3

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Next message: Artem Savkov: "Re: [PATCH 1/2] sun4i_ss_prng: fix return value of sun4i_ss_prng_generate"
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In reply to: Dave Martin: "Re: [PATCH 2/2] arm64: Expose Arm v8.4 features"
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