tools/testing/selftests/powerpc/tm/tm-unavailable.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright 2017, Gustavo Romero, Breno Leitao, Cyril Bur, IBM Corp.
  *
  * Force FP, VEC and VSX unavailable exception during transaction in all
  * possible scenarios regarding the MSR.FP and MSR.VEC state, e.g. when FP
  * is enable and VEC is disable, when FP is disable and VEC is enable, and
  * so on. Then we check if the restored state is correctly set for the
  * FP and VEC registers to the previous state we set just before we entered
  * in TM, i.e. we check if it corrupts somehow the recheckpointed FP and
  * VEC/Altivec registers on abortion due to an unavailable exception in TM.
  * N.B. In this test we do not test all the FP/Altivec/VSX registers for
  * corruption, but only for registers vs0 and vs32, which are respectively
  * representatives of FP and VEC/Altivec reg sets.
  */

 #define _GNU_SOURCE
 #include <error.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <inttypes.h>
 #include <stdbool.h>
 #include <pthread.h>
 #include <sched.h>

 #include "tm.h"

 #define DEBUG 0

 /* Unavailable exceptions to test in HTM */
 #define FP_UNA_EXCEPTION	0
 #define VEC_UNA_EXCEPTION	1
 #define VSX_UNA_EXCEPTION	2

 #define NUM_EXCEPTIONS		3
 #define err_at_line(status, errnum, format, ...) \
 	error_at_line(status, errnum,  __FILE__, __LINE__, format ##__VA_ARGS__)

 #define pr_warn(code, format, ...) err_at_line(0, code, format, ##__VA_ARGS__)
 #define pr_err(code, format, ...) err_at_line(1, code, format, ##__VA_ARGS__)

 struct Flags {
 	int touch_fp;
 	int touch_vec;
 	int result;
 	int exception;
 } flags;

 bool expecting_failure(void)
 {
 	if (flags.touch_fp && flags.exception == FP_UNA_EXCEPTION)
 		return false;

 	if (flags.touch_vec && flags.exception == VEC_UNA_EXCEPTION)
 		return false;

 	/*
 	 * If both FP and VEC are touched it does not mean that touching VSX
 	 * won't raise an exception. However since FP and VEC state are already
 	 * correctly loaded, the transaction is not aborted (i.e.
 	 * treclaimed/trecheckpointed) and MSR.VSX is just set as 1, so a TM
 	 * failure is not expected also in this case.
 	 */
 	if ((flags.touch_fp && flags.touch_vec) &&
 	     flags.exception == VSX_UNA_EXCEPTION)
 		return false;

 	return true;
 }

 /* Check if failure occurred whilst in transaction. */
 bool is_failure(uint64_t condition_reg)
 {
 	/*
 	 * When failure handling occurs, CR0 is set to 0b1010 (0xa). Otherwise
 	 * transaction completes without failure and hence reaches out 'tend.'
 	 * that sets CR0 to 0b0100 (0x4).
 	 */
 	return ((condition_reg >> 28) & 0xa) == 0xa;
 }

 void *tm_una_ping(void *input)
 {

 	/*
 	 * Expected values for vs0 and vs32 after a TM failure. They must never
 	 * change, otherwise they got corrupted.
 	 */
 	uint64_t high_vs0 = 0x5555555555555555;
 	uint64_t low_vs0 = 0xffffffffffffffff;
 	uint64_t high_vs32 = 0x5555555555555555;
 	uint64_t low_vs32 = 0xffffffffffffffff;

 	/* Counter for busy wait */
 	uint64_t counter = 0x1ff000000;

 	/*
 	 * Variable to keep a copy of CR register content taken just after we
 	 * leave the transactional state.
 	 */
 	uint64_t cr_ = 0;

 	/*
 	 * Wait a bit so thread can get its name "ping". This is not important
 	 * to reproduce the issue but it's nice to have for systemtap debugging.
 	 */
 	if (DEBUG)
 		sleep(1);

 	printf("If MSR.FP=%d MSR.VEC=%d: ", flags.touch_fp, flags.touch_vec);

 	if (flags.exception != FP_UNA_EXCEPTION &&
 	    flags.exception != VEC_UNA_EXCEPTION &&
 	    flags.exception != VSX_UNA_EXCEPTION) {
 		printf("No valid exception specified to test.\n");
 		return NULL;
 	}

 	asm (
 		/* Prepare to merge low and high. */
 		"	mtvsrd		33, %[high_vs0]		;"
 		"	mtvsrd		34, %[low_vs0]		;"

 		/*
 		 * Adjust VS0 expected value after an TM failure,
 		 * i.e. vs0 = 0x5555555555555555555FFFFFFFFFFFFFFFF
 		 */
 		"	xxmrghd		0, 33, 34		;"

 		/*
 		 * Adjust VS32 expected value after an TM failure,
 		 * i.e. vs32 = 0x5555555555555555555FFFFFFFFFFFFFFFF
 		 */
 		"	xxmrghd		32, 33, 34		;"

 		/*
 		 * Wait an amount of context switches so load_fp and load_vec
 		 * overflow and MSR.FP, MSR.VEC, and MSR.VSX become zero (off).
 		 */
 		"	mtctr		%[counter]		;"

 		/* Decrement CTR branch if CTR non zero. */
 		"1:	bdnz 1b					;"

 		/*
 		 * Check if we want to touch FP prior to the test in order
 		 * to set MSR.FP = 1 before provoking an unavailable
 		 * exception in TM.
 		 */
 		"	cmpldi		%[touch_fp], 0		;"
 		"	beq		no_fp			;"
 		"	fadd		10, 10, 10		;"
 		"no_fp:						;"

 		/*
 		 * Check if we want to touch VEC prior to the test in order
 		 * to set MSR.VEC = 1 before provoking an unavailable
 		 * exception in TM.
 		 */
 		"	cmpldi		%[touch_vec], 0		;"
 		"	beq		no_vec			;"
 		"	vaddcuw		10, 10, 10		;"
 		"no_vec:					;"

 		/*
 		 * Perhaps it would be a better idea to do the
 		 * compares outside transactional context and simply
 		 * duplicate code.
 		 */
 		"	tbegin.					;"
 		"	beq		trans_fail		;"

 		/* Do we do FP Unavailable? */
 		"	cmpldi		%[exception], %[ex_fp]	;"
 		"	bne		1f			;"
 		"	fadd		10, 10, 10		;"
 		"	b		done			;"

 		/* Do we do VEC Unavailable? */
 		"1:	cmpldi		%[exception], %[ex_vec]	;"
 		"	bne		2f			;"
 		"	vaddcuw		10, 10, 10		;"
 		"	b		done			;"

 		/*
 		 * Not FP or VEC, therefore VSX. Ensure this
 		 * instruction always generates a VSX Unavailable.
 		 * ISA 3.0 is tricky here.
 		 * (xxmrghd will on ISA 2.07 and ISA 3.0)
 		 */
 		"2:	xxmrghd		10, 10, 10		;"

 		"done:	tend. ;"

 		"trans_fail: ;"

 		/* Give values back to C. */
 		"	mfvsrd		%[high_vs0], 0		;"
 		"	xxsldwi		3, 0, 0, 2		;"
 		"	mfvsrd		%[low_vs0], 3		;"
 		"	mfvsrd		%[high_vs32], 32	;"
 		"	xxsldwi		3, 32, 32, 2		;"
 		"	mfvsrd		%[low_vs32], 3		;"

 		/* Give CR back to C so that it can check what happened. */
 		"	mfcr		%[cr_]		;"

 		: [high_vs0]  "+r" (high_vs0),
 		  [low_vs0]   "+r" (low_vs0),
 		  [high_vs32] "=r" (high_vs32),
 		  [low_vs32]  "=r" (low_vs32),
 		  [cr_]       "+r" (cr_)
 		: [touch_fp]  "r"  (flags.touch_fp),
 		  [touch_vec] "r"  (flags.touch_vec),
 		  [exception] "r"  (flags.exception),
 		  [ex_fp]     "i"  (FP_UNA_EXCEPTION),
 		  [ex_vec]    "i"  (VEC_UNA_EXCEPTION),
 		  [ex_vsx]    "i"  (VSX_UNA_EXCEPTION),
 		  [counter]   "r"  (counter)

 		: "cr0", "ctr", "v10", "vs0", "vs10", "vs3", "vs32", "vs33",
 		  "vs34", "fr10"

 		);

 	/*
 	 * Check if we were expecting a failure and it did not occur by checking
 	 * CR0 state just after we leave the transaction. Either way we check if
 	 * vs0 or vs32 got corrupted.
 	 */
 	if (expecting_failure() && !is_failure(cr_)) {
 		printf("\n\tExpecting the transaction to fail, %s",
 			"but it didn't\n\t");
 		flags.result++;
 	}

 	/* Check if we were not expecting a failure and a it occurred. */
 	if (!expecting_failure() && is_failure(cr_) &&
 	    !failure_is_reschedule()) {
 		printf("\n\tUnexpected transaction failure 0x%02lx\n\t",
 			failure_code());
 		return (void *) -1;
 	}

 	/*
 	 * Check if TM failed due to the cause we were expecting. 0xda is a
 	 * TM_CAUSE_FAC_UNAV cause, otherwise it's an unexpected cause, unless
 	 * it was caused by a reschedule.
 	 */
 	if (is_failure(cr_) && !failure_is_unavailable() &&
 	    !failure_is_reschedule()) {
 		printf("\n\tUnexpected failure cause 0x%02lx\n\t",
 			failure_code());
 		return (void *) -1;
 	}

 	/* 0x4 is a success and 0xa is a fail. See comment in is_failure(). */
 	if (DEBUG)
 		printf("CR0: 0x%1lx ", cr_ >> 28);

 	/* Check FP (vs0) for the expected value. */
 	if (high_vs0 != 0x5555555555555555 || low_vs0 != 0xFFFFFFFFFFFFFFFF) {
 		printf("FP corrupted!");
 			printf("  high = %#16" PRIx64 "  low = %#16" PRIx64 " ",
 				high_vs0, low_vs0);
 		flags.result++;
 	} else
 		printf("FP ok ");

 	/* Check VEC (vs32) for the expected value. */
 	if (high_vs32 != 0x5555555555555555 || low_vs32 != 0xFFFFFFFFFFFFFFFF) {
 		printf("VEC corrupted!");
 			printf("  high = %#16" PRIx64 "  low = %#16" PRIx64,
 				high_vs32, low_vs32);
 		flags.result++;
 	} else
 		printf("VEC ok");

 	putchar('\n');

 	return NULL;
 }

 /* Thread to force context switch */
 void *tm_una_pong(void *not_used)
 {
 	/* Wait thread get its name "pong". */
 	if (DEBUG)
 		sleep(1);

 	/* Classed as an interactive-like thread. */
 	while (1)
 		sched_yield();
 }

 /* Function that creates a thread and launches the "ping" task. */
 void test_fp_vec(int fp, int vec, pthread_attr_t *attr)
 {
 	int retries = 2;
 	void *ret_value;
 	pthread_t t0;

 	flags.touch_fp = fp;
 	flags.touch_vec = vec;

 	/*
 	 * Without luck it's possible that the transaction is aborted not due to
 	 * the unavailable exception caught in the middle as we expect but also,
 	 * for instance, due to a context switch or due to a KVM reschedule (if
 	 * it's running on a VM). Thus we try a few times before giving up,
 	 * checking if the failure cause is the one we expect.
 	 */
 	do {
 		int rc;

 		/* Bind to CPU 0, as specified in 'attr'. */
 		rc = pthread_create(&t0, attr, tm_una_ping, (void *) &flags);
 		if (rc)
 			pr_err(rc, "pthread_create()");
 		rc = pthread_setname_np(t0, "tm_una_ping");
 		if (rc)
 			pr_warn(rc, "pthread_setname_np");
 		rc = pthread_join(t0, &ret_value);
 		if (rc)
 			pr_err(rc, "pthread_join");

 		retries--;
 	} while (ret_value != NULL && retries);

 	if (!retries) {
 		flags.result = 1;
 		if (DEBUG)
 			printf("All transactions failed unexpectedly\n");

 	}
 }

 int tm_unavailable_test(void)
 {
 	int cpu, rc, exception; /* FP = 0, VEC = 1, VSX = 2 */
 	pthread_t t1;
 	pthread_attr_t attr;
 	cpu_set_t cpuset;

 	SKIP_IF(!have_htm());

 	cpu = pick_online_cpu();
 	FAIL_IF(cpu < 0);

 	// Set only one CPU in the mask. Both threads will be bound to that CPU.
 	CPU_ZERO(&cpuset);
 	CPU_SET(cpu, &cpuset);

 	/* Init pthread attribute. */
 	rc = pthread_attr_init(&attr);
 	if (rc)
 		pr_err(rc, "pthread_attr_init()");

 	/* Set CPU 0 mask into the pthread attribute. */
 	rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
 	if (rc)
 		pr_err(rc, "pthread_attr_setaffinity_np()");

 	rc = pthread_create(&t1, &attr /* Bind to CPU 0 */, tm_una_pong, NULL);
 	if (rc)
 		pr_err(rc, "pthread_create()");

 	/* Name it for systemtap convenience */
 	rc = pthread_setname_np(t1, "tm_una_pong");
 	if (rc)
 		pr_warn(rc, "pthread_create()");

 	flags.result = 0;

 	for (exception = 0; exception < NUM_EXCEPTIONS; exception++) {
 		printf("Checking if FP/VEC registers are sane after");

 		if (exception == FP_UNA_EXCEPTION)
 			printf(" a FP unavailable exception...\n");

 		else if (exception == VEC_UNA_EXCEPTION)
 			printf(" a VEC unavailable exception...\n");

 		else
 			printf(" a VSX unavailable exception...\n");

 		flags.exception = exception;

 		test_fp_vec(0, 0, &attr);
 		test_fp_vec(1, 0, &attr);
 		test_fp_vec(0, 1, &attr);
 		test_fp_vec(1, 1, &attr);

 	}

 	if (flags.result > 0) {
 		printf("result: failed!\n");
 		exit(1);
 	} else {
 		printf("result: success\n");
 		exit(0);
 	}
 }

 int main(int argc, char **argv)
 {
 	test_harness_set_timeout(220);
 	return test_harness(tm_unavailable_test, "tm_unavailable_test");
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright 2017, Gustavo Romero, Breno Leitao, Cyril Bur, IBM Corp.
	*
	* Force FP, VEC and VSX unavailable exception during transaction in all
	* possible scenarios regarding the MSR.FP and MSR.VEC state, e.g. when FP
	* is enable and VEC is disable, when FP is disable and VEC is enable, and
	* so on. Then we check if the restored state is correctly set for the
	* FP and VEC registers to the previous state we set just before we entered
	* in TM, i.e. we check if it corrupts somehow the recheckpointed FP and
	* VEC/Altivec registers on abortion due to an unavailable exception in TM.
	* N.B. In this test we do not test all the FP/Altivec/VSX registers for
	* corruption, but only for registers vs0 and vs32, which are respectively
	* representatives of FP and VEC/Altivec reg sets.
	*/

	#define _GNU_SOURCE
	#include <error.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <inttypes.h>
	#include <stdbool.h>
	#include <pthread.h>
	#include <sched.h>

	#include "tm.h"

	#define DEBUG 0

	/* Unavailable exceptions to test in HTM */
	#define FP_UNA_EXCEPTION 0
	#define VEC_UNA_EXCEPTION 1
	#define VSX_UNA_EXCEPTION 2

	#define NUM_EXCEPTIONS 3
	#define err_at_line(status, errnum, format, ...) \
	error_at_line(status, errnum, __FILE__, __LINE__, format ##__VA_ARGS__)

	#define pr_warn(code, format, ...) err_at_line(0, code, format, ##__VA_ARGS__)
	#define pr_err(code, format, ...) err_at_line(1, code, format, ##__VA_ARGS__)

	struct Flags {
	int touch_fp;
	int touch_vec;
	int result;
	int exception;
	} flags;

	bool expecting_failure(void)
	{
	if (flags.touch_fp && flags.exception == FP_UNA_EXCEPTION)
	return false;

	if (flags.touch_vec && flags.exception == VEC_UNA_EXCEPTION)
	return false;

	/*
	* If both FP and VEC are touched it does not mean that touching VSX
	* won't raise an exception. However since FP and VEC state are already
	* correctly loaded, the transaction is not aborted (i.e.
	* treclaimed/trecheckpointed) and MSR.VSX is just set as 1, so a TM
	* failure is not expected also in this case.
	*/
	if ((flags.touch_fp && flags.touch_vec) &&
	flags.exception == VSX_UNA_EXCEPTION)
	return false;

	return true;
	}

	/* Check if failure occurred whilst in transaction. */
	bool is_failure(uint64_t condition_reg)
	{
	/*
	* When failure handling occurs, CR0 is set to 0b1010 (0xa). Otherwise
	* transaction completes without failure and hence reaches out 'tend.'
	* that sets CR0 to 0b0100 (0x4).
	*/
	return ((condition_reg >> 28) & 0xa) == 0xa;
	}

	void tm_una_ping(void input)
	{

	/*
	* Expected values for vs0 and vs32 after a TM failure. They must never
	* change, otherwise they got corrupted.
	*/
	uint64_t high_vs0 = 0x5555555555555555;
	uint64_t low_vs0 = 0xffffffffffffffff;
	uint64_t high_vs32 = 0x5555555555555555;
	uint64_t low_vs32 = 0xffffffffffffffff;

	/* Counter for busy wait */
	uint64_t counter = 0x1ff000000;

	/*
	* Variable to keep a copy of CR register content taken just after we
	* leave the transactional state.
	*/
	uint64_t cr_ = 0;

	/*
	* Wait a bit so thread can get its name "ping". This is not important
	* to reproduce the issue but it's nice to have for systemtap debugging.
	*/
	if (DEBUG)
	sleep(1);

	printf("If MSR.FP=%d MSR.VEC=%d: ", flags.touch_fp, flags.touch_vec);

	if (flags.exception != FP_UNA_EXCEPTION &&
	flags.exception != VEC_UNA_EXCEPTION &&
	flags.exception != VSX_UNA_EXCEPTION) {
	printf("No valid exception specified to test.\n");
	return NULL;
	}

	asm (
	/* Prepare to merge low and high. */
	" mtvsrd 33, %[high_vs0] ;"
	" mtvsrd 34, %[low_vs0] ;"

	/*
	* Adjust VS0 expected value after an TM failure,
	* i.e. vs0 = 0x5555555555555555555FFFFFFFFFFFFFFFF
	*/
	" xxmrghd 0, 33, 34 ;"

	/*
	* Adjust VS32 expected value after an TM failure,
	* i.e. vs32 = 0x5555555555555555555FFFFFFFFFFFFFFFF
	*/
	" xxmrghd 32, 33, 34 ;"

	/*
	* Wait an amount of context switches so load_fp and load_vec
	* overflow and MSR.FP, MSR.VEC, and MSR.VSX become zero (off).
	*/
	" mtctr %[counter] ;"

	/* Decrement CTR branch if CTR non zero. */
	"1: bdnz 1b ;"

	/*
	* Check if we want to touch FP prior to the test in order
	* to set MSR.FP = 1 before provoking an unavailable
	* exception in TM.
	*/
	" cmpldi %[touch_fp], 0 ;"
	" beq no_fp ;"
	" fadd 10, 10, 10 ;"
	"no_fp: ;"

	/*
	* Check if we want to touch VEC prior to the test in order
	* to set MSR.VEC = 1 before provoking an unavailable
	* exception in TM.
	*/
	" cmpldi %[touch_vec], 0 ;"
	" beq no_vec ;"
	" vaddcuw 10, 10, 10 ;"
	"no_vec: ;"

	/*
	* Perhaps it would be a better idea to do the
	* compares outside transactional context and simply
	* duplicate code.
	*/
	" tbegin. ;"
	" beq trans_fail ;"

	/* Do we do FP Unavailable? */
	" cmpldi %[exception], %[ex_fp] ;"
	" bne 1f ;"
	" fadd 10, 10, 10 ;"
	" b done ;"

	/* Do we do VEC Unavailable? */
	"1: cmpldi %[exception], %[ex_vec] ;"
	" bne 2f ;"
	" vaddcuw 10, 10, 10 ;"
	" b done ;"

	/*
	* Not FP or VEC, therefore VSX. Ensure this
	* instruction always generates a VSX Unavailable.
	* ISA 3.0 is tricky here.
	* (xxmrghd will on ISA 2.07 and ISA 3.0)
	*/
	"2: xxmrghd 10, 10, 10 ;"

	"done: tend. ;"

	"trans_fail: ;"

	/* Give values back to C. */
	" mfvsrd %[high_vs0], 0 ;"
	" xxsldwi 3, 0, 0, 2 ;"
	" mfvsrd %[low_vs0], 3 ;"
	" mfvsrd %[high_vs32], 32 ;"
	" xxsldwi 3, 32, 32, 2 ;"
	" mfvsrd %[low_vs32], 3 ;"

	/* Give CR back to C so that it can check what happened. */
	" mfcr %[cr_] ;"

	: [high_vs0] "+r" (high_vs0),
	[low_vs0] "+r" (low_vs0),
	[high_vs32] "=r" (high_vs32),
	[low_vs32] "=r" (low_vs32),
	[cr_] "+r" (cr_)
	: [touch_fp] "r" (flags.touch_fp),
	[touch_vec] "r" (flags.touch_vec),
	[exception] "r" (flags.exception),
	[ex_fp] "i" (FP_UNA_EXCEPTION),
	[ex_vec] "i" (VEC_UNA_EXCEPTION),
	[ex_vsx] "i" (VSX_UNA_EXCEPTION),
	[counter] "r" (counter)

	: "cr0", "ctr", "v10", "vs0", "vs10", "vs3", "vs32", "vs33",
	"vs34", "fr10"

	);

	/*
	* Check if we were expecting a failure and it did not occur by checking
	* CR0 state just after we leave the transaction. Either way we check if
	* vs0 or vs32 got corrupted.
	*/
	if (expecting_failure() && !is_failure(cr_)) {
	printf("\n\tExpecting the transaction to fail, %s",
	"but it didn't\n\t");
	flags.result++;
	}

	/* Check if we were not expecting a failure and a it occurred. */
	if (!expecting_failure() && is_failure(cr_) &&
	!failure_is_reschedule()) {
	printf("\n\tUnexpected transaction failure 0x%02lx\n\t",
	failure_code());
	return (void *) -1;
	}

	/*
	* Check if TM failed due to the cause we were expecting. 0xda is a
	* TM_CAUSE_FAC_UNAV cause, otherwise it's an unexpected cause, unless
	* it was caused by a reschedule.
	*/
	if (is_failure(cr_) && !failure_is_unavailable() &&
	!failure_is_reschedule()) {
	printf("\n\tUnexpected failure cause 0x%02lx\n\t",
	failure_code());
	return (void *) -1;
	}

	/* 0x4 is a success and 0xa is a fail. See comment in is_failure(). */
	if (DEBUG)
	printf("CR0: 0x%1lx ", cr_ >> 28);

	/* Check FP (vs0) for the expected value. */
	if (high_vs0 != 0x5555555555555555 \|\| low_vs0 != 0xFFFFFFFFFFFFFFFF) {
	printf("FP corrupted!");
	printf(" high = %#16" PRIx64 " low = %#16" PRIx64 " ",
	high_vs0, low_vs0);
	flags.result++;
	} else
	printf("FP ok ");

	/* Check VEC (vs32) for the expected value. */
	if (high_vs32 != 0x5555555555555555 \|\| low_vs32 != 0xFFFFFFFFFFFFFFFF) {
	printf("VEC corrupted!");
	printf(" high = %#16" PRIx64 " low = %#16" PRIx64,
	high_vs32, low_vs32);
	flags.result++;
	} else
	printf("VEC ok");

	putchar('\n');

	return NULL;
	}

	/* Thread to force context switch */
	void tm_una_pong(void not_used)
	{
	/* Wait thread get its name "pong". */
	if (DEBUG)
	sleep(1);

	/* Classed as an interactive-like thread. */
	while (1)
	sched_yield();
	}

	/* Function that creates a thread and launches the "ping" task. */
	void test_fp_vec(int fp, int vec, pthread_attr_t *attr)
	{
	int retries = 2;
	void *ret_value;
	pthread_t t0;

	flags.touch_fp = fp;
	flags.touch_vec = vec;

	/*
	* Without luck it's possible that the transaction is aborted not due to
	* the unavailable exception caught in the middle as we expect but also,
	* for instance, due to a context switch or due to a KVM reschedule (if
	* it's running on a VM). Thus we try a few times before giving up,
	* checking if the failure cause is the one we expect.
	*/
	do {
	int rc;

	/* Bind to CPU 0, as specified in 'attr'. */
	rc = pthread_create(&t0, attr, tm_una_ping, (void *) &flags);
	if (rc)
	pr_err(rc, "pthread_create()");
	rc = pthread_setname_np(t0, "tm_una_ping");
	if (rc)
	pr_warn(rc, "pthread_setname_np");
	rc = pthread_join(t0, &ret_value);
	if (rc)
	pr_err(rc, "pthread_join");

	retries--;
	} while (ret_value != NULL && retries);

	if (!retries) {
	flags.result = 1;
	if (DEBUG)
	printf("All transactions failed unexpectedly\n");

	}
	}

	int tm_unavailable_test(void)
	{
	int cpu, rc, exception; /* FP = 0, VEC = 1, VSX = 2 */
	pthread_t t1;
	pthread_attr_t attr;
	cpu_set_t cpuset;

	SKIP_IF(!have_htm());

	cpu = pick_online_cpu();
	FAIL_IF(cpu < 0);

	// Set only one CPU in the mask. Both threads will be bound to that CPU.
	CPU_ZERO(&cpuset);
	CPU_SET(cpu, &cpuset);

	/* Init pthread attribute. */
	rc = pthread_attr_init(&attr);
	if (rc)
	pr_err(rc, "pthread_attr_init()");

	/* Set CPU 0 mask into the pthread attribute. */
	rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
	if (rc)
	pr_err(rc, "pthread_attr_setaffinity_np()");

	rc = pthread_create(&t1, &attr /* Bind to CPU 0 */, tm_una_pong, NULL);
	if (rc)
	pr_err(rc, "pthread_create()");

	/* Name it for systemtap convenience */
	rc = pthread_setname_np(t1, "tm_una_pong");
	if (rc)
	pr_warn(rc, "pthread_create()");

	flags.result = 0;

	for (exception = 0; exception < NUM_EXCEPTIONS; exception++) {
	printf("Checking if FP/VEC registers are sane after");

	if (exception == FP_UNA_EXCEPTION)
	printf(" a FP unavailable exception...\n");

	else if (exception == VEC_UNA_EXCEPTION)
	printf(" a VEC unavailable exception...\n");

	else
	printf(" a VSX unavailable exception...\n");

	flags.exception = exception;

	test_fp_vec(0, 0, &attr);
	test_fp_vec(1, 0, &attr);
	test_fp_vec(0, 1, &attr);
	test_fp_vec(1, 1, &attr);

	}

	if (flags.result > 0) {
	printf("result: failed!\n");
	exit(1);
	} else {
	printf("result: success\n");
	exit(0);
	}
	}

	int main(int argc, char **argv)
	{
	test_harness_set_timeout(220);
	return test_harness(tm_unavailable_test, "tm_unavailable_test");
	}