[PATCH v1 19/38] arm64/sme: Implement vector length configuration prctl()s

[Mark Brown]

As for SVE provide a prctl() interface which allows processes to
configure their SME vector length.

Signed-off-by: Mark Brown <broonie at kernel.org>
---
 arch/arm64/include/asm/processor.h   |  4 +++-
 arch/arm64/include/asm/thread_info.h |  1 +
 arch/arm64/kernel/fpsimd.c           | 30 ++++++++++++++++++++++++++++
 include/uapi/linux/prctl.h           |  9 +++++++++
 kernel/sys.c                         |  6 ++++++
 5 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 575a1fe719b7..a62d2f8045bf 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -354,9 +354,11 @@ extern void __init minsigstksz_setup(void);
  */
 #include <asm/fpsimd.h>
 
-/* Userspace interface for PR_SVE_{SET,GET}_VL prctl()s: */
+/* Userspace interface for PR_S[MV]E_{SET,GET}_VL prctl()s: */
 #define SVE_SET_VL(arg)	sve_set_current_vl(arg)
 #define SVE_GET_VL()	sve_get_current_vl()
+#define SME_SET_VL(arg)	sme_set_current_vl(arg)
+#define SME_GET_VL()	sme_get_current_vl()
 
 /* PR_PAC_RESET_KEYS prctl */
 #define PAC_RESET_KEYS(tsk, arg)	ptrauth_prctl_reset_keys(tsk, arg)
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index d5c8ac81ce11..5c4355204f4a 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -81,6 +81,7 @@ int arch_dup_task_struct(struct task_struct *dst,
 #define TIF_SVE_VL_INHERIT	24	/* Inherit SVE vl_onexec across exec */
 #define TIF_SSBD		25	/* Wants SSB mitigation */
 #define TIF_TAGGED_ADDR		26	/* Allow tagged user addresses */
+#define TIF_SME_VL_INHERIT	28	/* Inherit SME vl_onexec across exec */
 
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 13df5920fe1e..9511428c2e81 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -145,6 +145,8 @@ static unsigned int vec_vl_inherit_flag(enum vec_type type)
 	switch (type) {
 	case ARM64_VEC_SVE:
 		return TIF_SVE_VL_INHERIT;
+	case ARM64_VEC_SME:
+		return TIF_SME_VL_INHERIT;
 	default:
 		WARN_ON_ONCE(1);
 		return 0;
@@ -800,6 +802,34 @@ int sve_get_current_vl(void)
 	return vec_prctl_status(ARM64_VEC_SVE, 0);
 }
 
+/* PR_SME_SET_VL */
+int sme_set_current_vl(unsigned long arg)
+{
+	unsigned long vl, flags;
+	int ret;
+
+	vl = arg & PR_SME_VL_LEN_MASK;
+	flags = arg & ~vl;
+
+	if (!system_supports_sme() || is_compat_task())
+		return -EINVAL;
+
+	ret = vec_set_vector_length(current, ARM64_VEC_SME, vl, flags);
+	if (ret)
+		return ret;
+
+	return vec_prctl_status(ARM64_VEC_SME, flags);
+}
+
+/* PR_SME_GET_VL */
+int sme_get_current_vl(void)
+{
+	if (!system_supports_sme() || is_compat_task())
+		return -EINVAL;
+
+	return vec_prctl_status(ARM64_VEC_SME, 0);
+}
+
 static void vec_probe_vqs(struct vl_info *info,
 			  DECLARE_BITMAP(map, SVE_VQ_MAX))
 {
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 43bd7f713c39..b3212d73c198 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -269,4 +269,13 @@ struct prctl_mm_map {
 # define PR_SCHED_CORE_SHARE_FROM	3 /* pull core_sched cookie to pid */
 # define PR_SCHED_CORE_MAX		4
 
+/* arm64 Scalable Matrix Extension controls */
+/* Flag values must be in sync with SVE versions */
+#define PR_SME_SET_VL			63	/* set task vector length */
+# define PR_SME_SET_VL_ONEXEC		(1 << 18) /* defer effect until exec */
+#define PR_SME_GET_VL			64	/* get task vector length */
+/* Bits common to PR_SME_SET_VL and PR_SME_GET_VL */
+# define PR_SME_VL_LEN_MASK		0xffff
+# define PR_SME_VL_INHERIT		(1 << 17) /* inherit across exec */
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 8fdac0d90504..bf45194ce03b 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2463,6 +2463,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	case PR_SVE_GET_VL:
 		error = SVE_GET_VL();
 		break;
+	case PR_SME_SET_VL:
+		error = SME_SET_VL(arg2);
+		break;
+	case PR_SME_GET_VL:
+		error = SME_GET_VL();
+		break;
 	case PR_GET_SPECULATION_CTRL:
 		if (arg3 || arg4 || arg5)
 			return -EINVAL;
-- 
2.20.1