path: root/man2/spu_run.2

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.\" HISTORY:
.\" 2005-09-28, created by Arnd Bergmann <arndb@de.ibm.com>
.\" 2006-06-16, revised by Eduardo M. Fleury <efleury@br.ibm.com>
.\" 2007-07-10, some polishing by mtk
.\" 2007-09-28, updates for newer kernels, added example
.\"             by Jeremy Kerr <jk@ozlabs.org>
.\"
.TH SPU_RUN 2 2020-11-01 Linux "Linux Programmer's Manual"
.SH NAME
spu_run \- execute an SPU context
.SH SYNOPSIS
.nf
.B #include <sys/spu.h>
.PP
.BI "int spu_run(int " fd ", unsigned int *" npc \
", unsigned int *" event ");"
.fi
.PP
.IR Note :
There is no glibc wrapper for this system call; see NOTES.
.SH DESCRIPTION
The
.BR 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
.I fd
argument is a file descriptor returned by
.BR 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
.IR npc .
.PP
Execution of SPU code happens synchronously, meaning that
.BR 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
.BR pthread_create (3)).
.PP
When
.BR spu_run ()
returns, the current value of the SPU program counter is written to
.IR npc ,
so successive calls to
.BR spu_run ()
can use the same
.I npc
pointer.
.PP
The
.I event
argument provides a buffer for an extended status code.
If the SPU
context was created with the
.B SPU_CREATE_EVENTS_ENABLED
flag, then this buffer is populated by the Linux kernel before
.BR spu_run ()
returns.
.PP
The status code may be one (or more) of the following constants:
.TP
.B SPE_EVENT_DMA_ALIGNMENT
A DMA alignment error occurred.
.TP
.B SPE_EVENT_INVALID_DMA
An invalid MFC DMA command was attempted.
.\" SPE_EVENT_SPE_DATA_SEGMENT is defined, but does not seem to be generated
.\" at any point (in Linux 5.9 sources).
.TP
.B SPE_EVENT_SPE_DATA_STORAGE
A DMA storage error occurred.
.TP
.B SPE_EVENT_SPE_ERROR
An illegal instruction was executed.
.PP
NULL
is a valid value for the
.I event
argument.
In this case, the events will not be reported to the calling process.
.SH RETURN VALUE
On success,
.BR spu_run ()
returns the value of the
.I spu_status
register.
On error, it returns \-1 and sets
.I errno
to one of the error codes listed below.
.PP
The
.I spu_status
register value is a bit mask of status codes and
optionally a 14-bit code returned from the
.BR stop-and-signal
instruction on the SPU.
The bit masks for the status codes
are:
.TP
.B 0x02
SPU was stopped by a
.BR stop-and-signal
instruction.
.TP
.B 0x04
SPU was stopped by a
.BR halt
instruction.
.TP
.B 0x08
SPU is waiting for a channel.
.TP
.B 0x10
SPU is in single-step mode.
.TP
.B 0x20
SPU has tried to execute an invalid instruction.
.TP
.B 0x40
SPU has tried to access an invalid channel.
.TP
.B 0x3fff0000
The bits masked with this value contain the code returned from a
.BR stop-and-signal
instruction.
These bits are valid only if the 0x02 bit is set.
.PP
If
.BR spu_run ()
has not returned an error, one or more bits among the lower eight
ones are always set.
.SH ERRORS
.TP
.B EBADF
.I fd
is not a valid file descriptor.
.TP
.B EFAULT
.I npc
is not a valid pointer, or
.I event
is non-NULL and an invalid pointer.
.TP
.B EINTR
A signal occurred while
.BR spu_run ()
was in progress; see
.BR signal (7).
The
.I npc
value has been updated to the new program counter value if
necessary.
.TP
.B EINVAL
.I fd
is not a valid file descriptor returned from
.BR spu_create (2).
.TP
.B ENOMEM
There was not enough memory available to handle a page fault
resulting from a Memory Flow Controller (MFC) direct memory access.
.TP
.B 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.
.SH VERSIONS
The
.BR spu_run ()
system call was added to Linux in kernel 2.6.16.
.SH CONFORMING TO
This call is Linux-specific and implemented only by the PowerPC
architecture.
Programs using this system call are not portable.
.SH NOTES
Glibc does not provide a wrapper for this system call; call it using
.BR syscall (2).
Note however, that
.BR 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
.UR http://www.bsc.es\:/projects\:/deepcomputing\:/linuxoncell/
.UE
for the recommended libraries.
.SH EXAMPLES
The following is an example of running a simple, one-instruction SPU
program with the
.BR spu_run ()
system call.
.PP
.EX
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>

#define handle_error(msg) \e
    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 \(aqstop 0x1234\(aq instruction to the SPU\(aqs
     * 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\en", spu_status);

    exit(EXIT_SUCCESS);
}
.EE
.\" .SH AUTHORS
.\" Arnd Bergmann <arndb@de.ibm.com>, Jeremy Kerr <jk@ozlabs.org>
.SH SEE ALSO
.BR close (2),
.BR spu_create (2),
.BR capabilities (7),
.BR spufs (7)