Commit e5ab8be6 authored by Cyril Bur's avatar Cyril Bur Committed by Michael Ellerman
Browse files

selftests/powerpc: Test preservation of FPU and VMX regs across preemption 



Loop in assembly checking the registers with many threads.

Signed-off-by: default avatarCyril Bur <cyrilbur@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 01127f1e

tools/testing/selftests/powerpc/math/.gitignore

+2 −0
Original line number Diff line number Diff line 
fpu_syscall

vmx_syscall

fpu_preempt

vmx_preempt

tools/testing/selftests/powerpc/math/Makefile

+4 −1
Original line number Diff line number Diff line 
TEST_PROGS := fpu_syscall vmx_syscall

TEST_PROGS := fpu_syscall fpu_preempt vmx_syscall vmx_preempt



all: $(TEST_PROGS)
@@ -6,7 +6,10 @@ $(TEST_PROGS): ../harness.c 
$(TEST_PROGS): CFLAGS += -O2 -g -pthread -m64 -maltivec



fpu_syscall: fpu_asm.S

fpu_preempt: fpu_asm.S



vmx_syscall: vmx_asm.S

vmx_preempt: vmx_asm.S



include ../../lib.mk

tools/testing/selftests/powerpc/math/fpu_asm.S

+37 −0
Original line number Diff line number Diff line
@@ -159,3 +159,40 @@ FUNC_START(test_fpu) 
	POP_BASIC_STACK(256)

	blr

FUNC_END(test_fpu)



# int preempt_fpu(double *darray, int *threads_running, int *running)

# On starting will (atomically) decrement not_ready as a signal that the FPU

# has been loaded with darray. Will proceed to check the validity of the FPU

# registers while running is not zero.

FUNC_START(preempt_fpu)

	PUSH_BASIC_STACK(256)

	std r3,STACK_FRAME_PARAM(0)(sp) # double *darray

	std r4,STACK_FRAME_PARAM(1)(sp) # int *threads_starting

	std r5,STACK_FRAME_PARAM(2)(sp) # int *running

	PUSH_FPU(STACK_FRAME_LOCAL(3,0))



	bl load_fpu

	nop



	sync

	# Atomic DEC

	ld r3,STACK_FRAME_PARAM(1)(sp)

1:	lwarx r4,0,r3

	addi r4,r4,-1

	stwcx. r4,0,r3

	bne- 1b



2:	ld r3,STACK_FRAME_PARAM(0)(sp)

	bl check_fpu

	nop

	cmpdi r3,0

	bne 3f

	ld r4,STACK_FRAME_PARAM(2)(sp)

	ld r5,0(r4)

	cmpwi r5,0

	bne 2b



3:	POP_FPU(STACK_FRAME_LOCAL(3,0))

	POP_BASIC_STACK(256)

	blr

FUNC_END(preempt_fpu)

tools/testing/selftests/powerpc/math/fpu_preempt.c

0 → 100644
+113 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2015, Cyril Bur, IBM Corp.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version

 * 2 of the License, or (at your option) any later version.

 *

 * This test attempts to see if the FPU registers change across preemption.

 * Two things should be noted here a) The check_fpu function in asm only checks

 * the non volatile registers as it is reused from the syscall test b) There is

 * no way to be sure preemption happened so this test just uses many threads

 * and a long wait. As such, a successful test doesn't mean much but a failure

 * is bad.

 */



#include <stdio.h>

#include <unistd.h>

#include <sys/syscall.h>

#include <sys/time.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <stdlib.h>

#include <pthread.h>



#include "utils.h"



/* Time to wait for workers to get preempted (seconds) */

#define PREEMPT_TIME 20

/*

 * Factor by which to multiply number of online CPUs for total number of

 * worker threads

 */

#define THREAD_FACTOR 8





__thread double darray[] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,

		     1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,

		     2.1};



int threads_starting;

int running;



extern void preempt_fpu(double *darray, int *threads_starting, int *running);



void *preempt_fpu_c(void *p)

{

	int i;

	srand(pthread_self());

	for (i = 0; i < 21; i++)

		darray[i] = rand();



	/* Test failed if it ever returns */

	preempt_fpu(darray, &threads_starting, &running);



	return p;

}



int test_preempt_fpu(void)

{

	int i, rc, threads;

	pthread_t *tids;



	threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;

	tids = malloc((threads) * sizeof(pthread_t));

	FAIL_IF(!tids);



	running = true;

	threads_starting = threads;

	for (i = 0; i < threads; i++) {

		rc = pthread_create(&tids[i], NULL, preempt_fpu_c, NULL);

		FAIL_IF(rc);

	}



	setbuf(stdout, NULL);

	/* Not really necessary but nice to wait for every thread to start */

	printf("\tWaiting for all workers to start...");

	while(threads_starting)

		asm volatile("": : :"memory");

	printf("done\n");



	printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);

	sleep(PREEMPT_TIME);

	printf("done\n");



	printf("\tStopping workers...");

	/*

	 * Working are checking this value every loop. In preempt_fpu 'cmpwi r5,0; bne 2b'.

	 * r5 will have loaded the value of running.

	 */

	running = 0;

	for (i = 0; i < threads; i++) {

		void *rc_p;

		pthread_join(tids[i], &rc_p);



		/*

		 * Harness will say the fail was here, look at why preempt_fpu

		 * returned

		 */

		if ((long) rc_p)

			printf("oops\n");

		FAIL_IF((long) rc_p);

	}

	printf("done\n");



	free(tids);

	return 0;

}



int main(int argc, char *argv[])

{

	return test_harness(test_preempt_fpu, "fpu_preempt");

}

tools/testing/selftests/powerpc/math/vmx_asm.S

+42 −2
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 


#include "../basic_asm.h"



# POS MUST BE 16 ALIGNED!

#define PUSH_VMX(pos,reg) \

	li	reg,pos; \

	stvx	v20,reg,sp; \
@@ -35,6 +36,7 @@ 
	addi	reg,reg,16; \

	stvx	v31,reg,sp;



# POS MUST BE 16 ALIGNED!

#define POP_VMX(pos,reg) \

	li	reg,pos; \

	lvx	v20,reg,sp; \
@@ -93,7 +95,7 @@ FUNC_END(load_vmx) 


# Should be safe from C, only touches r4, r5 and v0,v1,v2

FUNC_START(check_vmx)

	PUSH_BASIC_STACK(16)

	PUSH_BASIC_STACK(32)

	mr r4,r3

	li	r3,1 # assume a bad result

	li	r5,0
@@ -162,7 +164,7 @@ FUNC_START(check_vmx) 
	cmpdi	r0,0xffffffffffffffff

	bne	1f

	li	r3,0

1:	POP_BASIC_STACK(16)

1:	POP_BASIC_STACK(32)

	blr

FUNC_END(check_vmx)
@@ -193,3 +195,41 @@ FUNC_START(test_vmx) 
	POP_BASIC_STACK(512)

	blr

FUNC_END(test_vmx)



# int preempt_vmx(vector int *varray, int *threads_starting, int *running)

# On starting will (atomically) decrement threads_starting as a signal that

# the VMX have been loaded with varray. Will proceed to check the validity of

# the VMX registers while running is not zero.

FUNC_START(preempt_vmx)

	PUSH_BASIC_STACK(512)

	std r3,STACK_FRAME_PARAM(0)(sp) # vector int *varray

	std r4,STACK_FRAME_PARAM(1)(sp) # int *threads_starting

	std r5,STACK_FRAME_PARAM(2)(sp) # int *running

	# VMX need to write to 16 byte aligned addresses, skip STACK_FRAME_LOCAL(3,0)

	PUSH_VMX(STACK_FRAME_LOCAL(4,0),r4)



	bl load_vmx

	nop



	sync

	# Atomic DEC

	ld r3,STACK_FRAME_PARAM(1)(sp)

1:	lwarx r4,0,r3

	addi r4,r4,-1

	stwcx. r4,0,r3

	bne- 1b



2:	ld r3,STACK_FRAME_PARAM(0)(sp)

	bl check_vmx

	nop

	cmpdi r3,0

	bne 3f

	ld r4,STACK_FRAME_PARAM(2)(sp)

	ld r5,0(r4)

	cmpwi r5,0

	bne 2b



3:	POP_VMX(STACK_FRAME_LOCAL(4,0),r4)

	POP_BASIC_STACK(512)

	blr

FUNC_END(preempt_vmx)