[{"id":1768575,"web_url":"http://patchwork.ozlabs.org/comment/1768575/","msgid":"<87a81xa0w5.fsf@linaro.org>","list_archive_url":null,"date":"2017-09-14T13:02:50","subject":"Re: [PATCH v2 20/28] arm64/sve: Add prctl controls for userspace\n\tvector length management","submitter":{"id":39532,"url":"http://patchwork.ozlabs.org/api/people/39532/","name":"Alex Bennée","email":"alex.bennee@linaro.org"},"content":"Dave Martin writes:\n\n> This patch adds two arm64-specific prctls, to permit userspace to\n> control its vector length:\n>\n> * PR_SVE_SET_VL: set the thread's SVE vector length and vector\n> length inheritance mode.\n>\n> * PR_SVE_GET_VL: get the same information.\n>\n> Although these calls shadow instruction set features in the SVE\n> architecture, these prctls provide additional control: the vector\n> length inheritance mode is Linux-specific and nothing to do with\n> the architecture, and the architecture does not permit EL0 to set\n> its own vector length directly. Both can be used in portable tools\n> without requiring the use of SVE instructions.\n>\n> Signed-off-by: Dave Martin \n\nReviewed-by: Alex Bennée \n\n> ---\n> arch/arm64/include/asm/fpsimd.h | 14 ++++++++++++\n> arch/arm64/include/asm/processor.h | 4 ++++\n> arch/arm64/kernel/fpsimd.c | 46 ++++++++++++++++++++++++++++++++++++++\n> include/uapi/linux/prctl.h | 4 ++++\n> kernel/sys.c | 12 ++++++++++\n> 5 files changed, 80 insertions(+)\n>\n> diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h\n> index 2723cca..d084968 100644\n> --- a/arch/arm64/include/asm/fpsimd.h\n> +++ b/arch/arm64/include/asm/fpsimd.h\n> @@ -17,6 +17,7 @@\n> #define __ASM_FP_H\n>\n> #include \n> +#include \n>\n> #ifndef __ASSEMBLY__\n>\n> @@ -99,6 +100,9 @@ extern void sve_sync_from_fpsimd_zeropad(struct task_struct *task);\n> extern int sve_set_vector_length(struct task_struct *task,\n> \t\t\t\t unsigned long vl, unsigned long flags);\n>\n> +extern int sve_set_current_vl(unsigned long arg);\n> +extern int sve_get_current_vl(void);\n> +\n> extern void __init sve_init_vq_map(void);\n> extern void sve_update_vq_map(void);\n> extern int sve_verify_vq_map(void);\n> @@ -114,6 +118,16 @@ static void __maybe_unused sve_sync_to_fpsimd(struct task_struct *task) { }\n> static void __maybe_unused sve_sync_from_fpsimd_zeropad(\n> \tstruct task_struct *task) { }\n>\n> +static int __maybe_unused sve_set_current_vl(unsigned long arg)\n> +{\n> +\treturn -EINVAL;\n> +}\n> +\n> +static int __maybe_unused sve_get_current_vl(void)\n> +{\n> +\treturn -EINVAL;\n> +}\n> +\n> static void __maybe_unused sve_init_vq_map(void) { }\n> static void __maybe_unused sve_update_vq_map(void) { }\n> static int __maybe_unused sve_verify_vq_map(void) { return 0; }\n> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h\n> index 3faceac..df66452 100644\n> --- a/arch/arm64/include/asm/processor.h\n> +++ b/arch/arm64/include/asm/processor.h\n> @@ -197,4 +197,8 @@ static inline void spin_lock_prefetch(const void *ptr)\n> int cpu_enable_pan(void *__unused);\n> int cpu_enable_cache_maint_trap(void *__unused);\n>\n> +/* Userspace interface for PR_SVE_{SET,GET}_VL prctl()s: */\n> +#define SVE_SET_VL(arg)\tsve_set_current_vl(arg)\n> +#define SVE_GET_VL()\tsve_get_current_vl()\n> +\n> #endif /* __ASM_PROCESSOR_H */\n> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c\n> index 361c019..42e8331 100644\n> --- a/arch/arm64/kernel/fpsimd.c\n> +++ b/arch/arm64/kernel/fpsimd.c\n> @@ -27,6 +27,7 @@\n> #include \n> #include \n> #include \n> +#include \n> #include \n> #include \n> #include \n> @@ -420,6 +421,51 @@ int sve_set_vector_length(struct task_struct *task,\n> \treturn 0;\n> }\n>\n> +/*\n> + * Encode the current vector length and flags for return.\n> + * This is only required for prctl(): ptrace has separate fields\n> + */\n> +static int sve_prctl_status(void)\n> +{\n> +\tint ret = current->thread.sve_vl;\n> +\n> +\tif (test_thread_flag(TIF_SVE_VL_INHERIT))\n> +\t\tret |= PR_SVE_VL_INHERIT;\n> +\n> +\treturn ret;\n> +}\n> +\n> +/* PR_SVE_SET_VL */\n> +int sve_set_current_vl(unsigned long arg)\n> +{\n> +\tunsigned long vl, flags;\n> +\tint ret;\n> +\n> +\tvl = arg & PR_SVE_VL_LEN_MASK;\n> +\tflags = arg & ~vl;\n> +\n> +\tif (!system_supports_sve())\n> +\t\treturn -EINVAL;\n> +\n> +\tpreempt_disable();\n> +\tret = sve_set_vector_length(current, vl, flags);\n> +\tpreempt_enable();\n> +\n> +\tif (ret)\n> +\t\treturn ret;\n> +\n> +\treturn sve_prctl_status();\n> +}\n> +\n> +/* PR_SVE_GET_VL */\n> +int sve_get_current_vl(void)\n> +{\n> +\tif (!system_supports_sve())\n> +\t\treturn -EINVAL;\n> +\n> +\treturn sve_prctl_status();\n> +}\n> +\n> static unsigned long *sve_alloc_vq_map(void)\n> {\n> \treturn kzalloc(BITS_TO_LONGS(SVE_VQ_MAX) * sizeof(unsigned long),\n> diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h\n> index 1b64901..1ef9370 100644\n> --- a/include/uapi/linux/prctl.h\n> +++ b/include/uapi/linux/prctl.h\n> @@ -198,7 +198,11 @@ struct prctl_mm_map {\n> # define PR_CAP_AMBIENT_CLEAR_ALL\t4\n>\n> /* arm64 Scalable Vector Extension controls */\n> +/* Flag values must be kept in sync with ptrace NT_ARM_SVE interface */\n> +#define PR_SVE_SET_VL\t\t\t48\t/* set task vector length */\n> # define PR_SVE_SET_VL_ONEXEC\t\t(1 << 18) /* defer effect until exec */\n> +#define PR_SVE_GET_VL\t\t\t49\t/* get task vector length */\n> +/* Bits common to PR_SVE_SET_VL and PR_SVE_GET_VL */\n> # define PR_SVE_VL_LEN_MASK\t\t0xffff\n> # define PR_SVE_VL_INHERIT\t\t(1 << 17) /* inherit across exec */\n>\n> diff --git a/kernel/sys.c b/kernel/sys.c\n> index 2855ee7..f8215a6 100644\n> --- a/kernel/sys.c\n> +++ b/kernel/sys.c\n> @@ -110,6 +110,12 @@\n> #ifndef SET_FP_MODE\n> # define SET_FP_MODE(a,b)\t(-EINVAL)\n> #endif\n> +#ifndef SVE_SET_VL\n> +# define SVE_SET_VL(a)\t\t(-EINVAL)\n> +#endif\n> +#ifndef SVE_GET_VL\n> +# define SVE_GET_VL()\t\t(-EINVAL)\n> +#endif\n>\n> /*\n> * this is where the system-wide overflow UID and GID are defined, for\n> @@ -2389,6 +2395,12 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,\n> \tcase PR_GET_FP_MODE:\n> \t\terror = GET_FP_MODE(me);\n> \t\tbreak;\n> +\tcase PR_SVE_SET_VL:\n> +\t\terror = SVE_SET_VL(arg2);\n> +\t\tbreak;\n> +\tcase PR_SVE_GET_VL:\n> +\t\terror = SVE_GET_VL();\n> +\t\tbreak;\n> \tdefault:\n> \t\terror = -EINVAL;\n> \t\tbreak;\n\n\n--\nAlex Bennée","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":["patchwork-incoming@bilbo.ozlabs.org","mailing list libc-alpha@sourceware.org"],"Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=sourceware.org\n\t(client-ip=209.132.180.131; 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emacs 25.2.50.3","From":"Alex =?utf-8?q?Benn=C3=A9e?= ","To":"Dave Martin ","Cc":"linux-arm-kernel@lists.infradead.org,\n\tCatalin Marinas ,\n\tWill Deacon ,\n\tArd Biesheuvel ,\n\tSzabolcs Nagy ,\n\tRichard Sandiford ,\n\tkvmarm@lists.cs.columbia.edu, libc-alpha@sourceware.org,\n\tlinux-arch@vger.kernel.org, Andrew Morton ","Subject":"Re: [PATCH v2 20/28] arm64/sve: Add prctl controls for userspace\n\tvector length management","In-reply-to":"<1504198860-12951-21-git-send-email-Dave.Martin@arm.com>","Date":"Thu, 14 Sep 2017 14:02:50 +0100","Message-ID":"<87a81xa0w5.fsf@linaro.org>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Transfer-Encoding":"8bit"}}]