1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2024 ARM Limited
4  *
5  * Common helper functions for SVE and SME functionality.
6  */
7 
8 #include <stdbool.h>
9 #include <kselftest.h>
10 #include <asm/sigcontext.h>
11 #include <sys/prctl.h>
12 
13 unsigned int vls[SVE_VQ_MAX];
14 unsigned int nvls;
15 
16 int sve_fill_vls(bool use_sme, int min_vls)
17 {
18 	int vq, vl;
19 	int pr_set_vl = use_sme ? PR_SME_SET_VL : PR_SVE_SET_VL;
20 	int len_mask = use_sme ? PR_SME_VL_LEN_MASK : PR_SVE_VL_LEN_MASK;
21 
22 	/*
23 	 * Enumerate up to SVE_VQ_MAX vector lengths
24 	 */
25 	for (vq = SVE_VQ_MAX; vq > 0; --vq) {
26 		vl = prctl(pr_set_vl, vq * 16);
27 		if (vl == -1)
28 			return KSFT_FAIL;
29 
30 		vl &= len_mask;
31 
32 		/*
33 		 * Unlike SVE, SME does not require the minimum vector length
34 		 * to be implemented, or the VLs to be consecutive, so any call
35 		 * to the prctl might return the single implemented VL, which
36 		 * might be larger than 16. So to avoid this loop never
37 		 * terminating,  bail out here when we find a higher VL than
38 		 * we asked for.
39 		 * See the ARM ARM, DDI 0487K.a, B1.4.2: I_QQRNR and I_NWYBP.
40 		 */
41 		if (vq < sve_vq_from_vl(vl))
42 			break;
43 
44 		/* Skip missing VLs */
45 		vq = sve_vq_from_vl(vl);
46 
47 		vls[nvls++] = vl;
48 	}
49 
50 	if (nvls < min_vls) {
51 		fprintf(stderr, "Only %d VL supported\n", nvls);
52 		return KSFT_SKIP;
53 	}
54 
55 	return KSFT_PASS;
56 }
57