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

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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 <cleger@xxxxxxxxxxxx>

---
  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 <atishp@xxxxxxxxxxxx>






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