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SPU_RUN(2) | Linux Programmer's Manual | SPU_RUN(2) |
NAME¶
spu_run - execute an SPU context
SYNOPSIS¶
#include <sys/spu.h> /* Definition of SPU_* constants */ #include <sys/syscall.h> /* Definition of SYS_* constants */ #include <unistd.h>
int spu_run(int fd, uint32_t *npc, uint32_t *event);
Note: glibc provides no wrapper for spu_run(), necessitating the use of syscall(2).
DESCRIPTION¶
The spu_run() system call is used on PowerPC machines that implement the Cell Broadband Engine Architecture in order to access Synergistic Processor Units (SPUs). The fd argument is a file descriptor returned by spu_create(2) that refers to a specific SPU context. When the context gets scheduled to a physical SPU, it starts execution at the instruction pointer passed in npc.
Execution of SPU code happens synchronously, meaning that spu_run() blocks while the SPU is still running. If there is a need to execute SPU code in parallel with other code on either the main CPU or other SPUs, a new thread of execution must be created first (e.g., using pthread_create(3)).
When spu_run() returns, the current value of the SPU program counter is written to npc, so successive calls to spu_run() can use the same npc pointer.
The event argument provides a buffer for an extended status code. If the SPU context was created with the SPU_CREATE_EVENTS_ENABLED flag, then this buffer is populated by the Linux kernel before spu_run() returns.
The status code may be one (or more) of the following constants:
- SPE_EVENT_DMA_ALIGNMENT
- A DMA alignment error occurred.
- SPE_EVENT_INVALID_DMA
- An invalid MFC DMA command was attempted.
- SPE_EVENT_SPE_DATA_STORAGE
- A DMA storage error occurred.
- SPE_EVENT_SPE_ERROR
- An illegal instruction was executed.
NULL is a valid value for the event argument. In this case, the events will not be reported to the calling process.
RETURN VALUE¶
On success, spu_run() returns the value of the spu_status register. On failure, it returns -1 and sets errno is set to indicate the error.
The spu_status register value is a bit mask of status codes and optionally a 14-bit code returned from the stop-and-signal instruction on the SPU. The bit masks for the status codes are:
- 0x02
- SPU was stopped by a stop-and-signal instruction.
- 0x04
- SPU was stopped by a halt instruction.
- 0x08
- SPU is waiting for a channel.
- 0x10
- SPU is in single-step mode.
- 0x20
- SPU has tried to execute an invalid instruction.
- 0x40
- SPU has tried to access an invalid channel.
- 0x3fff0000
- The bits masked with this value contain the code returned from a stop-and-signal instruction. These bits are valid only if the 0x02 bit is set.
If spu_run() has not returned an error, one or more bits among the lower eight ones are always set.
ERRORS¶
- EBADF
- fd is not a valid file descriptor.
- EFAULT
- npc is not a valid pointer, or event is non-NULL and an invalid pointer.
- EINTR
- A signal occurred while spu_run() was in progress; see signal(7). The npc value has been updated to the new program counter value if necessary.
- EINVAL
- fd is not a valid file descriptor returned from spu_create(2).
- ENOMEM
- There was not enough memory available to handle a page fault resulting from a Memory Flow Controller (MFC) direct memory access.
- ENOSYS
- The functionality is not provided by the current system, because either the hardware does not provide SPUs or the spufs module is not loaded.
VERSIONS¶
The spu_run() system call was added to Linux in kernel 2.6.16.
CONFORMING TO¶
This call is Linux-specific and implemented only by the PowerPC architecture. Programs using this system call are not portable.
NOTES¶
spu_run() is meant to be used from libraries that implement a more abstract interface to SPUs, not to be used from regular applications. See http://www.bsc.es/projects/deepcomputing/linuxoncell/ for the recommended libraries.
EXAMPLES¶
The following is an example of running a simple, one-instruction SPU program with the spu_run() system call.
#include <stdlib.h> #include <stdint.h> #include <unistd.h> #include <stdio.h> #include <sys/types.h> #include <fcntl.h> #define handle_error(msg) \
do { perror(msg); exit(EXIT_FAILURE); } while (0) int main(void) {
int context, fd, spu_status;
uint32_t instruction, npc;
context = spu_create("/spu/example-context", 0, 0755);
if (context == -1)
handle_error("spu_create");
/*
* Write a 'stop 0x1234' instruction to the SPU's
* local store memory.
*/
instruction = 0x00001234;
fd = open("/spu/example-context/mem", O_RDWR);
if (fd == -1)
handle_error("open");
write(fd, &instruction, sizeof(instruction));
/*
* set npc to the starting instruction address of the
* SPU program. Since we wrote the instruction at the
* start of the mem file, the entry point will be 0x0.
*/
npc = 0;
spu_status = spu_run(context, &npc, NULL);
if (spu_status == -1)
handle_error("open");
/*
* We should see a status code of 0x1234002:
* 0x00000002 (spu was stopped due to stop-and-signal)
* | 0x12340000 (the stop-and-signal code)
*/
printf("SPU Status: %#08x\n", spu_status);
exit(EXIT_SUCCESS); }
SEE ALSO¶
COLOPHON¶
This page is part of release 5.13 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
2021-03-22 | Linux |