2024-02-19 15:49:29

by Clément Léger

Subject: [PATCH] riscv: hwprobe: export Zihintpause ISA extension

Export the Zihintpause ISA extension through hwprobe which allows using
"pause" instructions. Some userspace applications (OpenJDK for
instance) uses this to handle some locking back-off.

Signed-off-by: Clément Léger <[email protected]>

---
Documentation/arch/riscv/hwprobe.rst | 4 ++++
arch/riscv/include/uapi/asm/hwprobe.h | 1 +
arch/riscv/kernel/sys_hwprobe.c | 1 +
3 files changed, 6 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index b2bcc9eed9aa..0012c8433613 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -188,6 +188,10 @@ The following keys are defined:
manual starting from commit 95cf1f9 ("Add changes requested by Ved
during signoff")

+ * :c:macro:`RISCV_HWPROBE_EXT_ZIHINTPAUSE`: The Zihintpause extension is
+ supported as defined in the RISC-V ISA manual starting from commit commit
+ d8ab5c78c207 ("Zihintpause is ratified").
+
* :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance
information about the selected set of processors.

diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 9f2a8e3ff204..31c570cbd1c5 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -59,6 +59,7 @@ struct riscv_hwprobe {
#define RISCV_HWPROBE_EXT_ZTSO (1ULL << 33)
#define RISCV_HWPROBE_EXT_ZACAS (1ULL << 34)
#define RISCV_HWPROBE_EXT_ZICOND (1ULL << 35)
+#define RISCV_HWPROBE_EXT_ZIHINTPAUSE (1ULL << 36)
#define RISCV_HWPROBE_KEY_CPUPERF_0 5
#define RISCV_HWPROBE_MISALIGNED_UNKNOWN (0 << 0)
#define RISCV_HWPROBE_MISALIGNED_EMULATED (1 << 0)
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index a7c56b41efd2..1008d25880e1 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -111,6 +111,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
EXT_KEY(ZTSO);
EXT_KEY(ZACAS);
EXT_KEY(ZICOND);
+ EXT_KEY(ZIHINTPAUSE);

if (has_vector()) {
EXT_KEY(ZVBB);
--
2.43.0

2024-02-20 23:43:15

by Atish Kumar Patra

Subject: Re: [PATCH] riscv: hwprobe: export Zihintpause ISA extension

On 2/19/24 07:49, Clément Léger wrote:
> Export the Zihintpause ISA extension through hwprobe which allows using
> "pause" instructions. Some userspace applications (OpenJDK for
> instance) uses this to handle some locking back-off.
>
> Signed-off-by: Clément Léger <[email protected]>
>
> ---
> Documentation/arch/riscv/hwprobe.rst | 4 ++++
> arch/riscv/include/uapi/asm/hwprobe.h | 1 +
> arch/riscv/kernel/sys_hwprobe.c | 1 +
> 3 files changed, 6 insertions(+)
>
> diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> index b2bcc9eed9aa..0012c8433613 100644
> --- a/Documentation/arch/riscv/hwprobe.rst
> +++ b/Documentation/arch/riscv/hwprobe.rst
> @@ -188,6 +188,10 @@ The following keys are defined:
> manual starting from commit 95cf1f9 ("Add changes requested by Ved
> during signoff")
>
> + * :c:macro:`RISCV_HWPROBE_EXT_ZIHINTPAUSE`: The Zihintpause extension is
> + supported as defined in the RISC-V ISA manual starting from commit commit
> + d8ab5c78c207 ("Zihintpause is ratified").
> +
> * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance
> information about the selected set of processors.
>
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index 9f2a8e3ff204..31c570cbd1c5 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -59,6 +59,7 @@ struct riscv_hwprobe {
> #define RISCV_HWPROBE_EXT_ZTSO (1ULL << 33)
> #define RISCV_HWPROBE_EXT_ZACAS (1ULL << 34)
> #define RISCV_HWPROBE_EXT_ZICOND (1ULL << 35)
> +#define RISCV_HWPROBE_EXT_ZIHINTPAUSE (1ULL << 36)
> #define RISCV_HWPROBE_KEY_CPUPERF_0 5
> #define RISCV_HWPROBE_MISALIGNED_UNKNOWN (0 << 0)
> #define RISCV_HWPROBE_MISALIGNED_EMULATED (1 << 0)
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index a7c56b41efd2..1008d25880e1 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -111,6 +111,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
> EXT_KEY(ZTSO);
> EXT_KEY(ZACAS);
> EXT_KEY(ZICOND);
> + EXT_KEY(ZIHINTPAUSE);
>
> if (has_vector()) {
> EXT_KEY(ZVBB);

Reviewed-by: Atish Patra <[email protected]>

2024-02-21 08:06:57

by Clément Léger

Subject: Re: [PATCH] riscv: hwprobe: export Zihintpause ISA extension

On 21/02/2024 00:42, Atish Patra wrote:
>          during signoff")
>   +  * :c:macro:`RISCV_HWPROBE_EXT_ZIHINTPAUSE`: The Zihintpause
> extension is
> +       supported as defined in the RISC-V ISA manual starting from
> commit commit

Looks like I did a typo ("commit" twice). Let me send a V2.

Clément

> +       d8ab5c78c207 ("Zihintpause is ratified").
> +