Dave Martin <[email protected]> writes: > This patch adds two arm64-specific prctls, to permit userspace to > control its vector length: > > * PR_SVE_SET_VL: set the thread's SVE vector length and vector > length inheritance mode. > > * PR_SVE_GET_VL: get the same information. > > Although these calls shadow instruction set features in the SVE > architecture, these prctls provide additional control: the vector > length inheritance mode is Linux-specific and nothing to do with > the architecture, and the architecture does not permit EL0 to set > its own vector length directly. Both can be used in portable tools > without requiring the use of SVE instructions. > > Signed-off-by: Dave Martin <[email protected]>
Reviewed-by: Alex Bennée <[email protected]> > --- > arch/arm64/include/asm/fpsimd.h | 14 ++++++++++++ > arch/arm64/include/asm/processor.h | 4 ++++ > arch/arm64/kernel/fpsimd.c | 46 > ++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/prctl.h | 4 ++++ > kernel/sys.c | 12 ++++++++++ > 5 files changed, 80 insertions(+) > > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h > index 2723cca..d084968 100644 > --- a/arch/arm64/include/asm/fpsimd.h > +++ b/arch/arm64/include/asm/fpsimd.h > @@ -17,6 +17,7 @@ > #define __ASM_FP_H > > #include <asm/ptrace.h> > +#include <asm/errno.h> > > #ifndef __ASSEMBLY__ > > @@ -99,6 +100,9 @@ extern void sve_sync_from_fpsimd_zeropad(struct > task_struct *task); > extern int sve_set_vector_length(struct task_struct *task, > unsigned long vl, unsigned long flags); > > +extern int sve_set_current_vl(unsigned long arg); > +extern int sve_get_current_vl(void); > + > extern void __init sve_init_vq_map(void); > extern void sve_update_vq_map(void); > extern int sve_verify_vq_map(void); > @@ -114,6 +118,16 @@ static void __maybe_unused sve_sync_to_fpsimd(struct > task_struct *task) { } > static void __maybe_unused sve_sync_from_fpsimd_zeropad( > struct task_struct *task) { } > > +static int __maybe_unused sve_set_current_vl(unsigned long arg) > +{ > + return -EINVAL; > +} > + > +static int __maybe_unused sve_get_current_vl(void) > +{ > + return -EINVAL; > +} > + > static void __maybe_unused sve_init_vq_map(void) { } > static void __maybe_unused sve_update_vq_map(void) { } > static int __maybe_unused sve_verify_vq_map(void) { return 0; } > diff --git a/arch/arm64/include/asm/processor.h > b/arch/arm64/include/asm/processor.h > index 3faceac..df66452 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -197,4 +197,8 @@ static inline void spin_lock_prefetch(const void *ptr) > int cpu_enable_pan(void *__unused); > int cpu_enable_cache_maint_trap(void *__unused); > > +/* Userspace interface for PR_SVE_{SET,GET}_VL prctl()s: */ > +#define SVE_SET_VL(arg) sve_set_current_vl(arg) > +#define SVE_GET_VL() sve_get_current_vl() > + > #endif /* __ASM_PROCESSOR_H */ > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c > index 361c019..42e8331 100644 > --- a/arch/arm64/kernel/fpsimd.c > +++ b/arch/arm64/kernel/fpsimd.c > @@ -27,6 +27,7 @@ > #include <linux/kernel.h> > #include <linux/init.h> > #include <linux/percpu.h> > +#include <linux/prctl.h> > #include <linux/preempt.h> > #include <linux/prctl.h> > #include <linux/ptrace.h> > @@ -420,6 +421,51 @@ int sve_set_vector_length(struct task_struct *task, > return 0; > } > > +/* > + * Encode the current vector length and flags for return. > + * This is only required for prctl(): ptrace has separate fields > + */ > +static int sve_prctl_status(void) > +{ > + int ret = current->thread.sve_vl; > + > + if (test_thread_flag(TIF_SVE_VL_INHERIT)) > + ret |= PR_SVE_VL_INHERIT; > + > + return ret; > +} > + > +/* PR_SVE_SET_VL */ > +int sve_set_current_vl(unsigned long arg) > +{ > + unsigned long vl, flags; > + int ret; > + > + vl = arg & PR_SVE_VL_LEN_MASK; > + flags = arg & ~vl; > + > + if (!system_supports_sve()) > + return -EINVAL; > + > + preempt_disable(); > + ret = sve_set_vector_length(current, vl, flags); > + preempt_enable(); > + > + if (ret) > + return ret; > + > + return sve_prctl_status(); > +} > + > +/* PR_SVE_GET_VL */ > +int sve_get_current_vl(void) > +{ > + if (!system_supports_sve()) > + return -EINVAL; > + > + return sve_prctl_status(); > +} > + > static unsigned long *sve_alloc_vq_map(void) > { > return kzalloc(BITS_TO_LONGS(SVE_VQ_MAX) * sizeof(unsigned long), > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index 1b64901..1ef9370 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -198,7 +198,11 @@ struct prctl_mm_map { > # define PR_CAP_AMBIENT_CLEAR_ALL 4 > > /* arm64 Scalable Vector Extension controls */ > +/* Flag values must be kept in sync with ptrace NT_ARM_SVE interface */ > +#define PR_SVE_SET_VL 48 /* set task vector > length */ > # define PR_SVE_SET_VL_ONEXEC (1 << 18) /* defer effect until > exec */ > +#define PR_SVE_GET_VL 49 /* get task vector > length */ > +/* Bits common to PR_SVE_SET_VL and PR_SVE_GET_VL */ > # define PR_SVE_VL_LEN_MASK 0xffff > # define PR_SVE_VL_INHERIT (1 << 17) /* inherit across exec */ > > diff --git a/kernel/sys.c b/kernel/sys.c > index 2855ee7..f8215a6 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -110,6 +110,12 @@ > #ifndef SET_FP_MODE > # define SET_FP_MODE(a,b) (-EINVAL) > #endif > +#ifndef SVE_SET_VL > +# define SVE_SET_VL(a) (-EINVAL) > +#endif > +#ifndef SVE_GET_VL > +# define SVE_GET_VL() (-EINVAL) > +#endif > > /* > * this is where the system-wide overflow UID and GID are defined, for > @@ -2389,6 +2395,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, > arg2, unsigned long, arg3, > case PR_GET_FP_MODE: > error = GET_FP_MODE(me); > break; > + case PR_SVE_SET_VL: > + error = SVE_SET_VL(arg2); > + break; > + case PR_SVE_GET_VL: > + error = SVE_GET_VL(); > + break; > default: > error = -EINVAL; > break; -- Alex Bennée _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
