Re: [PATCH 10/13] riscv: hwprobe: Add thead vendor extension probing

From: Evan Green
Date: Mon Jun 10 2024 - 12:57:26 EST

On Sun, Jun 9, 2024 at 9:45 PM Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote:
>
> Add a new hwprobe key "RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0" which
> allows userspace to probe for the new RISCV_ISA_VENDOR_EXT_XTHEADVECTOR
> vendor extension.
>
> This new key will allow userspace code to probe for which thead vendor
> extensions are supported. This API is modeled to be consistent with
> RISCV_HWPROBE_KEY_IMA_EXT_0. The bitmask returned will have each bit
> corresponding to a supported thead vendor extension of the cpumask set.
> Just like RISCV_HWPROBE_KEY_IMA_EXT_0, this allows a userspace program
> to determine all of the supported thead vendor extensions in one call.
>
> Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> Reviewed-by: Evan Green <evan@xxxxxxxxxxxx>

You can continue to keep my tag, but I came up with some nits to pick anyway.

> ---
> arch/riscv/include/asm/hwprobe.h | 4 +--
> .../include/asm/vendor_extensions/thead_hwprobe.h | 18 +++++++++++
> .../include/asm/vendor_extensions/vendor_hwprobe.h | 37 ++++++++++++++++++++++
> arch/riscv/include/uapi/asm/hwprobe.h | 3 +-
> arch/riscv/include/uapi/asm/vendor/thead.h | 3 ++
> arch/riscv/kernel/sys_hwprobe.c | 5 +++
> arch/riscv/kernel/vendor_extensions/Makefile | 1 +
> .../riscv/kernel/vendor_extensions/thead_hwprobe.c | 19 +++++++++++
> 8 files changed, 87 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
> index 630507dff5ea..e68496b4f8de 100644
> --- a/arch/riscv/include/asm/hwprobe.h
> +++ b/arch/riscv/include/asm/hwprobe.h
> @@ -1,6 +1,6 @@
> /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> /*
> - * Copyright 2023 Rivos, Inc
> + * Copyright 2023-2024 Rivos, Inc
> */
>
> #ifndef _ASM_HWPROBE_H
> @@ -8,7 +8,7 @@
>
> #include <uapi/asm/hwprobe.h>
>
> -#define RISCV_HWPROBE_MAX_KEY 6
> +#define RISCV_HWPROBE_MAX_KEY 7
>
> static inline bool riscv_hwprobe_key_is_valid(__s64 key)
> {
> diff --git a/arch/riscv/include/asm/vendor_extensions/thead_hwprobe.h b/arch/riscv/include/asm/vendor_extensions/thead_hwprobe.h
> new file mode 100644
> index 000000000000..925fef39a2c0
> --- /dev/null
> +++ b/arch/riscv/include/asm/vendor_extensions/thead_hwprobe.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_RISCV_VENDOR_EXTENSIONS_THEAD_HWPROBE_H
> +#define _ASM_RISCV_VENDOR_EXTENSIONS_THEAD_HWPROBE_H
> +
> +#include <linux/cpumask.h>
> +
> +#include <uapi/asm/hwprobe.h>
> +
> +#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_THEAD
> +void hwprobe_isa_vendor_ext_thead_0(struct riscv_hwprobe *pair, const struct cpumask *cpus);
> +#else
> +static inline void hwprobe_isa_vendor_ext_thead_0(struct riscv_hwprobe *pair, const struct cpumask *cpus)
> +{
> + pair->value = 0;
> +}
> +#endif
> +
> +#endif
> diff --git a/arch/riscv/include/asm/vendor_extensions/vendor_hwprobe.h b/arch/riscv/include/asm/vendor_extensions/vendor_hwprobe.h
> new file mode 100644
> index 000000000000..b6222e7b519e
> --- /dev/null
> +++ b/arch/riscv/include/asm/vendor_extensions/vendor_hwprobe.h
> @@ -0,0 +1,37 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright 2024 Rivos, Inc
> + */
> +
> +#ifndef _ASM_RISCV_SYS_HWPROBE_H
> +#define _ASM_RISCV_SYS_HWPROBE_H
> +
> +#include <asm/cpufeature.h>
> +
> +#define EXT_KEY(ext) \

Nit: Do you think it should be VENDOR_EXT_KEY? I had a slight ping of
worry that the identifier sounds so generic it might conflict with
something later, but meh maybe it's fine.


> + do { \
> + if (__riscv_isa_extension_available(isainfo->isa, RISCV_ISA_VENDOR_EXT_##ext)) \
> + pair->value |= RISCV_HWPROBE_VENDOR_EXT_##ext; \
> + else \
> + missing |= RISCV_HWPROBE_VENDOR_EXT_##ext; \
> + } while (false)
> +
> +/*
> + * Loop through and record extensions that 1) anyone has, and 2) anyone
> + * doesn't have.
> + *
> + * _extension_checks is an arbitrary C block to set the values of pair->value
> + * and missing. It should be filled with EXT_KEY expressions.
> + */
> +#define VENDOR_EXTENSION_SUPPORTED(pair, cpus, per_hart_thead_bitmap, _extension_checks) \

Nit: This macro was meant to be generic for all vendors, but you've
named one of the parameters per_hart_thead_bitmap. :)

> + do { \
> + int cpu; \
> + u64 missing; \
> + for_each_cpu(cpu, (cpus)) { \
> + struct riscv_isavendorinfo *isainfo = &(per_hart_thead_bitmap)[cpu]; \
> + _extension_checks \
> + } \
> + (pair)->value &= ~missing; \
> + } while (false) \
> +
> +#endif /* _ASM_RISCV_SYS_HWPROBE_H */
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index dda76a05420b..155a83dd1cdf 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -1,6 +1,6 @@
> /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> /*
> - * Copyright 2023 Rivos, Inc
> + * Copyright 2023-2024 Rivos, Inc
> */
>
> #ifndef _UAPI_ASM_HWPROBE_H
> @@ -68,6 +68,7 @@ struct riscv_hwprobe {
> #define RISCV_HWPROBE_MISALIGNED_UNSUPPORTED (4 << 0)
> #define RISCV_HWPROBE_MISALIGNED_MASK (7 << 0)
> #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE 6
> +#define RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0 7
> /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
>
> /* Flags */
> diff --git a/arch/riscv/include/uapi/asm/vendor/thead.h b/arch/riscv/include/uapi/asm/vendor/thead.h
> new file mode 100644
> index 000000000000..43790ebe5faf
> --- /dev/null
> +++ b/arch/riscv/include/uapi/asm/vendor/thead.h
> @@ -0,0 +1,3 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +
> +#define RISCV_HWPROBE_VENDOR_EXT_XTHEADVECTOR (1 << 0)
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index 969ef3d59dbe..e39fa70083d3 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -13,6 +13,7 @@
> #include <asm/uaccess.h>
> #include <asm/unistd.h>
> #include <asm/vector.h>
> +#include <asm/vendor_extensions/thead_hwprobe.h>
> #include <vdso/vsyscall.h>
>
>
> @@ -217,6 +218,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
> pair->value = riscv_cboz_block_size;
> break;
>
> + case RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0:
> + hwprobe_isa_vendor_ext_thead_0(pair, cpus);
> + break;
> +
> /*
> * For forward compatibility, unknown keys don't fail the whole
> * call, but get their element key set to -1 and value set to 0
> diff --git a/arch/riscv/kernel/vendor_extensions/Makefile b/arch/riscv/kernel/vendor_extensions/Makefile
> index 353522cb3bf0..866414c81a9f 100644
> --- a/arch/riscv/kernel/vendor_extensions/Makefile
> +++ b/arch/riscv/kernel/vendor_extensions/Makefile
> @@ -2,3 +2,4 @@
>
> obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_ANDES) += andes.o
> obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_THEAD) += thead.o
> +obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_THEAD) += thead_hwprobe.o
> diff --git a/arch/riscv/kernel/vendor_extensions/thead_hwprobe.c b/arch/riscv/kernel/vendor_extensions/thead_hwprobe.c
> new file mode 100644
> index 000000000000..53f65942f7e8
> --- /dev/null
> +++ b/arch/riscv/kernel/vendor_extensions/thead_hwprobe.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <asm/vendor_extensions/thead.h>
> +#include <asm/vendor_extensions/thead_hwprobe.h>
> +#include <asm/vendor_extensions/vendor_hwprobe.h>
> +
> +#include <linux/cpumask.h>
> +#include <linux/types.h>
> +
> +#include <uapi/asm/hwprobe.h>
> +#include <uapi/asm/vendor/thead.h>
> +
> +void hwprobe_isa_vendor_ext_thead_0(struct riscv_hwprobe *pair, const struct cpumask *cpus)
> +{
> + VENDOR_EXTENSION_SUPPORTED(pair, cpus,
> + riscv_isa_vendor_ext_list_thead.per_hart_isa_bitmap, {
> + EXT_KEY(XTHEADVECTOR);
> + });
> +}
>
> --
> 2.44.0
>