Unverified Commit 00e76e2c authored by Evan Green's avatar Evan Green Committed by Palmer Dabbelt
Browse files

RISC-V: hwprobe: Add support for RISCV_HWPROBE_BASE_BEHAVIOR_IMA 



We have an implicit set of base behaviors that userspace depends on,
which are mostly defined in various ISA specifications.

Co-developed-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: default avatarEvan Green <evan@rivosinc.com>
Reviewed-by: default avatarConor Dooley <conor.dooley@microchip.com>
Reviewed-by: default avatarHeiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: default avatarHeiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: default avatarPaul Walmsley <paul.walmsley@sifive.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-4-evan@rivosinc.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent ea3de9ce

Documentation/riscv/hwprobe.rst

+24 −0
Original line number Diff line number Diff line
@@ -39,3 +39,27 @@ The following keys are defined: 


* :c:macro:`RISCV_HWPROBE_KEY_MIMPLID`: Contains the value of ``mimplid``, as

  defined by the RISC-V privileged architecture specification.



* :c:macro:`RISCV_HWPROBE_KEY_BASE_BEHAVIOR`: A bitmask containing the base

  user-visible behavior that this kernel supports.  The following base user ABIs

  are defined:



  * :c:macro:`RISCV_HWPROBE_BASE_BEHAVIOR_IMA`: Support for rv32ima or

    rv64ima, as defined by version 2.2 of the user ISA and version 1.10 of the

    privileged ISA, with the following known exceptions (more exceptions may be

    added, but only if it can be demonstrated that the user ABI is not broken):



    * The :fence.i: instruction cannot be directly executed by userspace

      programs (it may still be executed in userspace via a

      kernel-controlled mechanism such as the vDSO).



* :c:macro:`RISCV_HWPROBE_KEY_IMA_EXT_0`: A bitmask containing the extensions

  that are compatible with the :c:macro:`RISCV_HWPROBE_BASE_BEHAVIOR_IMA`:

  base system behavior.



  * :c:macro:`RISCV_HWPROBE_IMA_FD`: The F and D extensions are supported, as

    defined by commit cd20cee ("FMIN/FMAX now implement

    minimumNumber/maximumNumber, not minNum/maxNum") of the RISC-V ISA manual.



  * :c:macro:`RISCV_HWPROBE_IMA_C`: The C extension is supported, as defined

    by version 2.2 of the RISC-V ISA manual.

arch/riscv/include/asm/hwprobe.h

+1 −1
Original line number Diff line number Diff line
@@ -8,6 +8,6 @@ 


#include <uapi/asm/hwprobe.h>



#define RISCV_HWPROBE_MAX_KEY 2

#define RISCV_HWPROBE_MAX_KEY 4



#endif

arch/riscv/include/uapi/asm/hwprobe.h

+5 −0
Original line number Diff line number Diff line
@@ -20,6 +20,11 @@ struct riscv_hwprobe { 
#define RISCV_HWPROBE_KEY_MVENDORID	0

#define RISCV_HWPROBE_KEY_MARCHID	1

#define RISCV_HWPROBE_KEY_MIMPID	2

#define RISCV_HWPROBE_KEY_BASE_BEHAVIOR	3

#define		RISCV_HWPROBE_BASE_BEHAVIOR_IMA	(1 << 0)

#define RISCV_HWPROBE_KEY_IMA_EXT_0	4

#define		RISCV_HWPROBE_IMA_FD		(1 << 0)

#define		RISCV_HWPROBE_IMA_C		(1 << 1)

/* Increase RISCV_HWPROBE_MAX_KEY when adding items. */



#endif

arch/riscv/kernel/sys_riscv.c

+20 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <asm/cacheflush.h>

#include <asm/hwprobe.h>

#include <asm/sbi.h>

#include <asm/switch_to.h>

#include <asm/uaccess.h>

#include <asm/unistd.h>

#include <asm-generic/mman-common.h>
@@ -125,6 +126,25 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair, 
	case RISCV_HWPROBE_KEY_MIMPID:

		hwprobe_arch_id(pair, cpus);

		break;

	/*

	 * The kernel already assumes that the base single-letter ISA

	 * extensions are supported on all harts, and only supports the

	 * IMA base, so just cheat a bit here and tell that to

	 * userspace.

	 */

	case RISCV_HWPROBE_KEY_BASE_BEHAVIOR:

		pair->value = RISCV_HWPROBE_BASE_BEHAVIOR_IMA;

		break;



	case RISCV_HWPROBE_KEY_IMA_EXT_0:

		pair->value = 0;

		if (has_fpu())

			pair->value |= RISCV_HWPROBE_IMA_FD;



		if (riscv_isa_extension_available(NULL, c))

			pair->value |= RISCV_HWPROBE_IMA_C;



		break;



	/*

	 * For forward compatibility, unknown keys don't fail the whole