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[Userspace LL] zephyr: cpu: turn cpu_get_id() into a system call#11079

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[Userspace LL] zephyr: cpu: turn cpu_get_id() into a system call #11079

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2 changes: 2 additions & 0 deletions zephyr/CMakeLists.txt
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Original file line numberDiff line numberDiff line change
Expand Up@@ -620,6 +620,8 @@ zephyr_library_sources_ifdef(CONFIG_SHELL
sof_shell.c
)

zephyr_syscall_header(include/sof/lib/cpu.h)
zephyr_library_sources_ifdef(CONFIG_USERSPACE syscall/cpu.c)
zephyr_syscall_header(${SOF_SRC_PATH}/include/sof/audio/module_adapter/module/generic.h)
zephyr_syscall_header(${SOF_SRC_PATH}/include/sof/lib/fast-get.h)
zephyr_syscall_header(${SOF_SRC_PATH}/include/sof/ipc/ipc_reply.h)
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27 changes: 27 additions & 0 deletions zephyr/include/sof/lib/cpu.h
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Expand Up@@ -40,13 +40,32 @@ void cpu_notify_state_exit(enum pm_state state);

#endif /* CONFIG_PM */

/*
* cpu_get_id() is exposed as a Zephyr system call so that user-mode
* threads (e.g. user-space LL pipelines) can query the current core
* id. The underlying arch_proc_id() reads a privileged special
* register (e.g. Xtensa PRID) which would fault if executed directly
* from user mode. In supervisor context the generated wrapper inlines
* the z_impl_cpu_get_id() body, so there is no overhead there.
*/
#if defined(CONFIG_SOF_FULL_ZEPHYR_APPLICATION)
__syscall int cpu_get_id(void);
#endif

/* let the compiler optimise when in single core mode */
#if CONFIG_MULTICORE && CONFIG_SMP

#if defined(CONFIG_SOF_FULL_ZEPHYR_APPLICATION)
static inline int z_impl_cpu_get_id(void)
{
return arch_proc_id();
}
#else
static inline int cpu_get_id(void)
{
return arch_proc_id();
}
#endif

static inline bool cpu_is_primary(int id)
{
Expand All@@ -73,7 +92,11 @@ int cpu_restore_secondary_cores(void);
int cpu_secondary_cores_prepare_d0ix(void);
#else

#if defined(CONFIG_SOF_FULL_ZEPHYR_APPLICATION)
static inline int z_impl_cpu_get_id(void) { return 0; };
#else
static inline int cpu_get_id(void) { return 0; };
#endif

static inline bool cpu_is_primary(int id) { return 1; };

Expand All@@ -93,6 +116,10 @@ static inline int cpu_secondary_cores_prepare_d0ix(void) { return 0; };

#endif /* CONFIG_MULTICORE && CONFIG_SMP */

#if defined(CONFIG_SOF_FULL_ZEPHYR_APPLICATION)
#include <zephyr/syscalls/cpu.h>
#endif

#endif

#endif /* __SOF_LIB_CPU_H__ */
22 changes: 22 additions & 0 deletions zephyr/syscall/cpu.c
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
// SPDX-License-Identifier: BSD-3-Clause
//
// Copyright(c) 2026 Intel Corporation.

#include <sof/lib/cpu.h>
#include <zephyr/kernel.h>
#include <zephyr/internal/syscall_handler.h>

/**
* \brief Userspace verification wrapper for cpu_get_id().
*
* The system call takes no arguments and passes no pointers, so no
* access validation is required; the call is simply forwarded to the
* implementation running in supervisor context.
*
* @return Id of the DSP core executing the call.
*/
static inline int z_vrfy_cpu_get_id(void)
{
return z_impl_cpu_get_id();
}
#include <zephyr/syscalls/cpu_get_id_mrsh.c>
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