1 // SPDX-License-Identifier: GPL-2.0
2 /* Test context switching to see if the DSCR SPR is correctly preserved
3 * when within a transaction.
4 *
5 * Note: We assume that the DSCR has been left at the default value (0)
6 * for all CPUs.
7 *
8 * Method:
9 *
10 * Set a value into the DSCR.
11 *
12 * Start a transaction, and suspend it (*).
13 *
14 * Hard loop checking to see if the transaction has become doomed.
15 *
16 * Now that we *may* have been preempted, record the DSCR and TEXASR SPRS.
17 *
18 * If the abort was because of a context switch, check the DSCR value.
19 * Otherwise, try again.
20 *
21 * (*) If the transaction is not suspended we can't see the problem because
22 * the transaction abort handler will restore the DSCR to it's checkpointed
23 * value before we regain control.
24 */
25
26 #include <inttypes.h>
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <assert.h>
30 #include <asm/tm.h>
31
32 #include "utils.h"
33 #include "tm.h"
34 #include "../pmu/lib.h"
35
36 #define SPRN_DSCR 0x03
37
38 int test_body(void)
39 {
40 uint64_t rv, dscr1 = 1, dscr2, texasr;
41
42 SKIP_IF(!have_htm());
43 SKIP_IF(htm_is_synthetic());
44
45 printf("Check DSCR TM context switch: ");
46 fflush(stdout);
47 for (;;) {
48 asm __volatile__ (
49 /* set a known value into the DSCR */
50 "ld 3, %[dscr1];"
51 "mtspr %[sprn_dscr], 3;"
52
53 "li %[rv], 1;"
54 /* start and suspend a transaction */
55 "tbegin.;"
56 "beq 1f;"
57 "tsuspend.;"
58
59 /* hard loop until the transaction becomes doomed */
60 "2: ;"
61 "tcheck 0;"
62 "bc 4, 0, 2b;"
63
64 /* record DSCR and TEXASR */
65 "mfspr 3, %[sprn_dscr];"
66 "std 3, %[dscr2];"
67 "mfspr 3, %[sprn_texasr];"
68 "std 3, %[texasr];"
69
70 "tresume.;"
71 "tend.;"
72 "li %[rv], 0;"
73 "1: ;"
74 : [rv]"=r"(rv), [dscr2]"=m"(dscr2), [texasr]"=m"(texasr)
75 : [dscr1]"m"(dscr1)
76 , [sprn_dscr]"i"(SPRN_DSCR), [sprn_texasr]"i"(SPRN_TEXASR)
77 : "memory", "r3"
78 );
79 assert(rv); /* make sure the transaction aborted */
80 if ((texasr >> 56) != TM_CAUSE_RESCHED) {
81 continue;
82 }
83 if (dscr2 != dscr1) {
84 printf(" FAIL\n");
85 return 1;
86 } else {
87 printf(" OK\n");
88 return 0;
89 }
90 }
91 }
92
93 static int tm_resched_dscr(void)
94 {
95 return eat_cpu(test_body);
96 }
97
98 int main(int argc, const char *argv[])
99 {
100 return test_harness(tm_resched_dscr, "tm_resched_dscr");
101 }
102
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