[PATCH v14 11/39] arm64/sme: Implement vector length configuration prctl()s

Mark Brown
2022-04-19T11:24:30Z

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

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/fpsimd.h | 4 ++++
arch/arm64/include/asm/processor.h | 4 +++-
arch/arm64/include/asm/thread_info.h | 1 +
arch/arm64/kernel/fpsimd.c | 32 ++++++++++++++++++++++++++++
include/uapi/linux/prctl.h | 9 ++++++++
kernel/sys.c | 12 +++++++++++
6 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 32cd682258d9..38fd6aab7feb 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -288,6 +288,8 @@ static inline int sme_max_virtualisable_vl(void)
}

extern unsigned int sme_get_vl(void);
+extern int sme_set_current_vl(unsigned long arg);
+extern int sme_get_current_vl(void);

#else

@@ -299,6 +301,8 @@ static inline void sme_setup(void) { }
static inline unsigned int sme_get_vl(void) { return 0; }
static inline int sme_max_vl(void) { return 0; }
static inline int sme_max_virtualisable_vl(void) { return 0; }
+static inline int sme_set_current_vl(unsigned long arg) { return -EINVAL; }
+static inline int sme_get_current_vl(void) { return -EINVAL; }

#endif /* ! CONFIG_ARM64_SME */

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index abf34a9c2eab..7a57cbff8a03 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -355,9 +355,11 @@ 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 e1317b7c4525..4e6b58dcd6f9 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -82,6 +82,7 @@ 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 754a96563f6f..39f44fcb9b99 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -149,6 +149,8 @@ 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;
@@ -807,6 +809,36 @@ int sve_get_current_vl(void)
return vec_prctl_status(ARM64_VEC_SVE, 0);
}

+#ifdef CONFIG_ARM64_SME
+/* 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);
+}
+#endif /* CONFIG_ARM64_SME */
+
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 e998764f0262..a5e06dcbba13 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -272,6 +272,15 @@ struct prctl_mm_map {
# define PR_SCHED_CORE_SCOPE_THREAD_GROUP 1
# define PR_SCHED_CORE_SCOPE_PROCESS_GROUP 2

+/* 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 */
+
#define PR_SET_VMA 0x53564d41
# define PR_SET_VMA_ANON_NAME 0

diff --git a/kernel/sys.c b/kernel/sys.c
index 374f83e95239..b911fa6d81ab 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -117,6 +117,12 @@
#ifndef SVE_GET_VL
# define SVE_GET_VL() (-EINVAL)
#endif
+#ifndef SME_SET_VL
+# define SME_SET_VL(a) (-EINVAL)
+#endif
+#ifndef SME_GET_VL
+# define SME_GET_VL() (-EINVAL)
+#endif
#ifndef PAC_RESET_KEYS
# define PAC_RESET_KEYS(a, b) (-EINVAL)
#endif
@@ -2541,6 +2547,12 @@ 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;
--
2.30.2