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SubjectRe: [PATCH v2] arm64: cpufeature: Export matrix and other features to userspace
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Hi Will,

It was pointed out to me that this patch conflicts with Anshuman's
patch[1] adding the BFloat16 support. I'd like your opinion on the best
way of handling this.

I originally extended the scope of Julien's original patch based on your
comment[2] on his patch:

So we probably want a patch bringing all of this up to speed, rather
than randomly advertising some features and not others.

So which outcome do you prefer:

* Splitting up the features into multiple patches, i.e. Anshuman's
BF16, followed by a version of Julien's Matrix, followed by the
remaining features SPECRES/DGH.

* A single patch adding everything in one go (i.e. this patch).

* Something else I haven't thought of.

Thanks,

Steve

[1]
https://lore.kernel.org/linux-arm-kernel/1576145232-8311-1-git-send-email-anshuman.khandual@arm.com/
[2]
http://lists.infradead.org/pipermail/linux-arm-kernel/2019-October/690350.html

On 16/12/2019 11:33, Steven Price wrote:
> Export the features introduced as part of ARMv8.6 exposed in the
> ID_AA64ISAR1_EL1 and ID_AA64ZFR0_EL1 registers. This introduces the
> Matrix features (ARMv8.2-I8MM, ARMv8.2-F64MM and ARMv8.2-F32MM) along
> with BFloat16 (Armv8.2-BF16), speculation invalidation (SPECRES) and
> Data Gathering Hint (ARMv8.0-DGH).
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> [Added other features in those registers]
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> This is a v2 of Julien's patch[1] extended to export all the new
> features contained within the ID_AA64ISAR1_EL1 and ID_AA64ZFR0_EL1
> registers.
>
> [1] https://lore.kernel.org/linux-arm-kernel/20191025171056.30641-1-julien.grall@arm.com/
>
> Documentation/arm64/cpu-feature-registers.rst | 16 ++++++++++
> Documentation/arm64/elf_hwcaps.rst | 31 +++++++++++++++++++
> arch/arm64/include/asm/hwcap.h | 8 +++++
> arch/arm64/include/asm/sysreg.h | 12 +++++++
> arch/arm64/include/uapi/asm/hwcap.h | 8 +++++
> arch/arm64/kernel/cpufeature.c | 20 ++++++++++++
> arch/arm64/kernel/cpuinfo.c | 8 +++++
> 7 files changed, 103 insertions(+)
>
> diff --git a/Documentation/arm64/cpu-feature-registers.rst b/Documentation/arm64/cpu-feature-registers.rst
> index b6e44884e3ad..5382981533f8 100644
> --- a/Documentation/arm64/cpu-feature-registers.rst
> +++ b/Documentation/arm64/cpu-feature-registers.rst
> @@ -200,6 +200,14 @@ infrastructure:
> +------------------------------+---------+---------+
> | Name | bits | visible |
> +------------------------------+---------+---------+
> + | I8MM | [55-52] | y |
> + +------------------------------+---------+---------+
> + | DGH | [51-48] | y |
> + +------------------------------+---------+---------+
> + | BF16 | [47-44] | y |
> + +------------------------------+---------+---------+
> + | SPECRES | [43-40] | y |
> + +------------------------------+---------+---------+
> | SB | [39-36] | y |
> +------------------------------+---------+---------+
> | FRINTTS | [35-32] | y |
> @@ -234,10 +242,18 @@ infrastructure:
> +------------------------------+---------+---------+
> | Name | bits | visible |
> +------------------------------+---------+---------+
> + | F64MM | [59-56] | y |
> + +------------------------------+---------+---------+
> + | F32MM | [55-52] | y |
> + +------------------------------+---------+---------+
> + | I8MM | [47-44] | y |
> + +------------------------------+---------+---------+
> | SM4 | [43-40] | y |
> +------------------------------+---------+---------+
> | SHA3 | [35-32] | y |
> +------------------------------+---------+---------+
> + | BF16 | [23-20] | y |
> + +------------------------------+---------+---------+
> | BitPerm | [19-16] | y |
> +------------------------------+---------+---------+
> | AES | [7-4] | y |
> diff --git a/Documentation/arm64/elf_hwcaps.rst b/Documentation/arm64/elf_hwcaps.rst
> index 7fa3d215ae6a..183ba86ad46e 100644
> --- a/Documentation/arm64/elf_hwcaps.rst
> +++ b/Documentation/arm64/elf_hwcaps.rst
> @@ -204,6 +204,37 @@ HWCAP2_FRINT
>
> Functionality implied by ID_AA64ISAR1_EL1.FRINTTS == 0b0001.
>
> +HWCAP2_SVEI8MM
> +
> + Functionality implied by ID_AA64ZFR0_EL1.I8MM == 0b0001.
> +
> +HWCAP2_SVEF32MM
> +
> + Functionality implied by ID_AA64ZFR0_EL1.F32MM == 0b0001.
> +
> +HWCAP2_SVEF64MM
> +
> + Functionality implied by ID_AA64ZFR0_EL1.F64MM == 0b0001.
> +
> +HWCAP2_SVEBF16
> +
> + Functionality implied by ID_AA64ZFR0_EL1.BF16 == 0b0001.
> +
> +HWCAP2_I8MM
> +
> + Functionality implied by ID_AA64ISAR1_EL1.I8MM == 0b0001.
> +
> +HWCAP2_BF16
> +
> + Functionality implied by ID_AA64ISAR1_EL1.BF16 == 0b0001.
> +
> +HWCAP2_DGH
> +
> + Functionality implied by ID_AA64ISAR1_EL1.DGH == 0b0001.
> +
> +HWCAP2_SPECRES
> +
> + Functionality implied by ID_AA64ISAR1_EL1.SPECRES == 0b0001.
>
> 4. Unused AT_HWCAP bits
> -----------------------
> diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
> index 3d2f2472a36c..ac7180b2c20b 100644
> --- a/arch/arm64/include/asm/hwcap.h
> +++ b/arch/arm64/include/asm/hwcap.h
> @@ -86,6 +86,14 @@
> #define KERNEL_HWCAP_SVESM4 __khwcap2_feature(SVESM4)
> #define KERNEL_HWCAP_FLAGM2 __khwcap2_feature(FLAGM2)
> #define KERNEL_HWCAP_FRINT __khwcap2_feature(FRINT)
> +#define KERNEL_HWCAP_SVEI8MM __khwcap2_feature(SVEI8MM)
> +#define KERNEL_HWCAP_SVEF32MM __khwcap2_feature(SVEF32MM)
> +#define KERNEL_HWCAP_SVEF64MM __khwcap2_feature(SVEF64MM)
> +#define KERNEL_HWCAP_SVEBF16 __khwcap2_feature(SVEBF16)
> +#define KERNEL_HWCAP_I8MM __khwcap2_feature(I8MM)
> +#define KERNEL_HWCAP_DGH __khwcap2_feature(DGH)
> +#define KERNEL_HWCAP_BF16 __khwcap2_feature(BF16)
> +#define KERNEL_HWCAP_SPECRES __khwcap2_feature(SPECRES)
>
> /*
> * This yields a mask that user programs can use to figure out what
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 6e919fafb43d..f56c4a02a127 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -553,6 +553,10 @@
> #define ID_AA64ISAR0_AES_SHIFT 4
>
> /* id_aa64isar1 */
> +#define ID_AA64ISAR1_I8MM_SHIFT 52
> +#define ID_AA64ISAR1_DGH_SHIFT 48
> +#define ID_AA64ISAR1_BF16_SHIFT 44
> +#define ID_AA64ISAR1_SPECRES_SHIFT 40
> #define ID_AA64ISAR1_SB_SHIFT 36
> #define ID_AA64ISAR1_FRINTTS_SHIFT 32
> #define ID_AA64ISAR1_GPI_SHIFT 28
> @@ -605,12 +609,20 @@
> #define ID_AA64PFR1_SSBS_PSTATE_INSNS 2
>
> /* id_aa64zfr0 */
> +#define ID_AA64ZFR0_F64MM_SHIFT 56
> +#define ID_AA64ZFR0_F32MM_SHIFT 52
> +#define ID_AA64ZFR0_I8MM_SHIFT 44
> #define ID_AA64ZFR0_SM4_SHIFT 40
> #define ID_AA64ZFR0_SHA3_SHIFT 32
> +#define ID_AA64ZFR0_BF16_SHIFT 20
> #define ID_AA64ZFR0_BITPERM_SHIFT 16
> #define ID_AA64ZFR0_AES_SHIFT 4
> #define ID_AA64ZFR0_SVEVER_SHIFT 0
>
> +#define ID_AA64ZFR0_F64MM 0x1
> +#define ID_AA64ZFR0_F32MM 0x1
> +#define ID_AA64ZFR0_I8MM 0x1
> +#define ID_AA64ZFR0_BF16 0x1
> #define ID_AA64ZFR0_SM4 0x1
> #define ID_AA64ZFR0_SHA3 0x1
> #define ID_AA64ZFR0_BITPERM 0x1
> diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
> index a1e72886b30c..8f3f1b66f7b2 100644
> --- a/arch/arm64/include/uapi/asm/hwcap.h
> +++ b/arch/arm64/include/uapi/asm/hwcap.h
> @@ -65,5 +65,13 @@
> #define HWCAP2_SVESM4 (1 << 6)
> #define HWCAP2_FLAGM2 (1 << 7)
> #define HWCAP2_FRINT (1 << 8)
> +#define HWCAP2_SVEI8MM (1 << 9)
> +#define HWCAP2_SVEF32MM (1 << 10)
> +#define HWCAP2_SVEF64MM (1 << 11)
> +#define HWCAP2_SVEBF16 (1 << 12)
> +#define HWCAP2_I8MM (1 << 13)
> +#define HWCAP2_BF16 (1 << 14)
> +#define HWCAP2_DGH (1 << 15)
> +#define HWCAP2_SPECRES (1 << 16)
>
> #endif /* _UAPI__ASM_HWCAP_H */
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 04cf64e9f0c9..bf9e9e09da0d 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -135,6 +135,10 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
> };
>
> static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
> + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_I8MM_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_DGH_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_BF16_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_SPECRES_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_SB_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_FRINTTS_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
> @@ -176,10 +180,18 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
> };
>
> static const struct arm64_ftr_bits ftr_id_aa64zfr0[] = {
> + ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> + FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_F64MM_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> + FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_F32MM_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> + FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_I8MM_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SM4_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_SHA3_SHIFT, 4, 0),
> + ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> + FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_BF16_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ZFR0_BITPERM_SHIFT, 4, 0),
> ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
> @@ -1651,6 +1663,10 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
> HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_LRCPC_SHIFT, FTR_UNSIGNED, 2, CAP_HWCAP, KERNEL_HWCAP_ILRCPC),
> HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_FRINTTS_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_FRINT),
> HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_SB_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_SB),
> + HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_SPECRES_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_SPECRES),
> + HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_BF16_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_BF16),
> + HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_DGH_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_DGH),
> + HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_I8MM_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_I8MM),
> HWCAP_CAP(SYS_ID_AA64MMFR2_EL1, ID_AA64MMFR2_AT_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, KERNEL_HWCAP_USCAT),
> #ifdef CONFIG_ARM64_SVE
> HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_SVE_SHIFT, FTR_UNSIGNED, ID_AA64PFR0_SVE, CAP_HWCAP, KERNEL_HWCAP_SVE),
> @@ -1658,8 +1674,12 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
> HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_AES_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_AES, CAP_HWCAP, KERNEL_HWCAP_SVEAES),
> HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_AES_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_AES_PMULL, CAP_HWCAP, KERNEL_HWCAP_SVEPMULL),
> HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_BITPERM_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_BITPERM, CAP_HWCAP, KERNEL_HWCAP_SVEBITPERM),
> + HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_BF16_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_BF16, CAP_HWCAP, KERNEL_HWCAP_SVEBF16),
> HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_SHA3_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_SHA3, CAP_HWCAP, KERNEL_HWCAP_SVESHA3),
> HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_SM4_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_SM4, CAP_HWCAP, KERNEL_HWCAP_SVESM4),
> + HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_I8MM_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_I8MM, CAP_HWCAP, KERNEL_HWCAP_SVEI8MM),
> + HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_F32MM_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_F32MM, CAP_HWCAP, KERNEL_HWCAP_SVEF32MM),
> + HWCAP_CAP(SYS_ID_AA64ZFR0_EL1, ID_AA64ZFR0_F64MM_SHIFT, FTR_UNSIGNED, ID_AA64ZFR0_F64MM, CAP_HWCAP, KERNEL_HWCAP_SVEF64MM),
> #endif
> HWCAP_CAP(SYS_ID_AA64PFR1_EL1, ID_AA64PFR1_SSBS_SHIFT, FTR_UNSIGNED, ID_AA64PFR1_SSBS_PSTATE_INSNS, CAP_HWCAP, KERNEL_HWCAP_SSBS),
> #ifdef CONFIG_ARM64_PTR_AUTH
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 56bba746da1c..1eaf4dc0c5a0 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -84,6 +84,14 @@ static const char *const hwcap_str[] = {
> "svesm4",
> "flagm2",
> "frint",
> + "svei8mm",
> + "svef32mm",
> + "svef64mm",
> + "svebf16",
> + "i8mm",
> + "bf16",
> + "dgh",
> + "specres",
> NULL
> };
>
>

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