jcs.org
qemu with hax to log dma reads & writes
jcs.org/2018/11/12/vfio
target/ppc: Clarify compat mode max_threads value
We recently had some discussions that were sidetracked for a while, because
nearly everyone misapprehended the purpose of the 'max_threads' field in
the compatiblity modes table. It's all about guest expectations, not host
expectations or support (that's handled elsewhere).
In an attempt to avoid a repeat of that confusion, rename the field to
'max_vthreads' and add an explanatory comment.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
+20
-11
+2
-2
hw/ppc/spapr.c
+2
-2
hw/ppc/spapr.c
···
345
345
PowerPCCPU *cpu = POWERPC_CPU(cs);
346
346
DeviceClass *dc = DEVICE_GET_CLASS(cs);
347
347
int index = spapr_vcpu_id(cpu);
348
-
int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));
348
+
int compat_smt = MIN(smp_threads, ppc_compat_max_vthreads(cpu));
349
349
350
350
if ((index % smt) != 0) {
351
351
continue;
···
503
503
size_t page_sizes_prop_size;
504
504
uint32_t vcpus_per_socket = smp_threads * smp_cores;
505
505
uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
506
-
int compat_smt = MIN(smp_threads, ppc_compat_max_threads(cpu));
506
+
int compat_smt = MIN(smp_threads, ppc_compat_max_vthreads(cpu));
507
507
sPAPRDRConnector *drc;
508
508
int drc_index;
509
509
uint32_t radix_AP_encodings[PPC_PAGE_SIZES_MAX_SZ];
+17
-8
target/ppc/compat.c
+17
-8
target/ppc/compat.c
···
32
32
uint32_t pvr;
33
33
uint64_t pcr;
34
34
uint64_t pcr_level;
35
-
int max_threads;
35
+
36
+
/*
37
+
* Maximum allowed virtual threads per virtual core
38
+
*
39
+
* This is to stop older guests getting confused by seeing more
40
+
* threads than they think the cpu can support. Usually it's
41
+
* equal to the number of threads supported on bare metal
42
+
* hardware, but not always (see POWER9).
43
+
*/
44
+
int max_vthreads;
36
45
} CompatInfo;
37
46
38
47
static const CompatInfo compat_table[] = {
···
45
54
.pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 |
46
55
PCR_COMPAT_2_05 | PCR_TM_DIS | PCR_VSX_DIS,
47
56
.pcr_level = PCR_COMPAT_2_05,
48
-
.max_threads = 2,
57
+
.max_vthreads = 2,
49
58
},
50
59
{ /* POWER7, ISA2.06 */
51
60
.name = "power7",
52
61
.pvr = CPU_POWERPC_LOGICAL_2_06,
53
62
.pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
54
63
.pcr_level = PCR_COMPAT_2_06,
55
-
.max_threads = 4,
64
+
.max_vthreads = 4,
56
65
},
57
66
{
58
67
.name = "power7+",
59
68
.pvr = CPU_POWERPC_LOGICAL_2_06_PLUS,
60
69
.pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_TM_DIS,
61
70
.pcr_level = PCR_COMPAT_2_06,
62
-
.max_threads = 4,
71
+
.max_vthreads = 4,
63
72
},
64
73
{ /* POWER8, ISA2.07 */
65
74
.name = "power8",
66
75
.pvr = CPU_POWERPC_LOGICAL_2_07,
67
76
.pcr = PCR_COMPAT_3_00 | PCR_COMPAT_2_07,
68
77
.pcr_level = PCR_COMPAT_2_07,
69
-
.max_threads = 8,
78
+
.max_vthreads = 8,
70
79
},
71
80
{ /* POWER9, ISA3.00 */
72
81
.name = "power9",
···
80
89
* confusing if half of the threads disappear from the guest
81
90
* if it announces it's POWER9 aware at CAS time.
82
91
*/
83
-
.max_threads = 8,
92
+
.max_vthreads = 8,
84
93
},
85
94
};
86
95
···
192
201
}
193
202
}
194
203
195
-
int ppc_compat_max_threads(PowerPCCPU *cpu)
204
+
int ppc_compat_max_vthreads(PowerPCCPU *cpu)
196
205
{
197
206
const CompatInfo *compat = compat_by_pvr(cpu->compat_pvr);
198
207
int n_threads = CPU(cpu)->nr_threads;
199
208
200
209
if (cpu->compat_pvr) {
201
210
g_assert(compat);
202
-
n_threads = MIN(n_threads, compat->max_threads);
211
+
n_threads = MIN(n_threads, compat->max_vthreads);
203
212
}
204
213
205
214
return n_threads;
+1
-1
target/ppc/cpu.h
+1
-1
target/ppc/cpu.h
···
1395
1395
#if !defined(CONFIG_USER_ONLY)
1396
1396
void ppc_set_compat_all(uint32_t compat_pvr, Error **errp);
1397
1397
#endif
1398
-
int ppc_compat_max_threads(PowerPCCPU *cpu);
1398
+
int ppc_compat_max_vthreads(PowerPCCPU *cpu);
1399
1399
void ppc_compat_add_property(Object *obj, const char *name,
1400
1400
uint32_t *compat_pvr, const char *basedesc,
1401
1401
Error **errp);