[PATCH 4.14 044/104] x86/cpu/topology: Provide detect_extended_topology_early()

From: Greg Kroah-Hartman
Date: Tue Aug 14 2018 - 13:35:33 EST


4.14-stable review patch. If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

commit 95f3d39ccf7aaea79d1ffdac1c887c2e100ec1b6 upstream

To support force disabling of SMT it's required to know the number of
thread siblings early. detect_extended_topology() cannot be called before
the APIC driver is selected, so split out the part which initializes
smp_num_siblings.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/cpu.h | 1 +
arch/x86/kernel/cpu/topology.c | 30 ++++++++++++++++++++++++------
2 files changed, 25 insertions(+), 6 deletions(-)

--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -47,6 +47,7 @@ extern const struct cpu_dev *const __x86

extern void get_cpu_cap(struct cpuinfo_x86 *c);
extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
+extern int detect_extended_topology_early(struct cpuinfo_x86 *c);
extern int detect_ht_early(struct cpuinfo_x86 *c);

unsigned int aperfmperf_get_khz(int cpu);
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -27,15 +27,13 @@
* exists, use it for populating initial_apicid and cpu topology
* detection.
*/
-void detect_extended_topology(struct cpuinfo_x86 *c)
+int detect_extended_topology_early(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
- unsigned int eax, ebx, ecx, edx, sub_index;
- unsigned int ht_mask_width, core_plus_mask_width;
- unsigned int core_select_mask, core_level_siblings;
+ unsigned int eax, ebx, ecx, edx;

if (c->cpuid_level < 0xb)
- return;
+ return -1;

cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);

@@ -43,7 +41,7 @@ void detect_extended_topology(struct cpu
* check if the cpuid leaf 0xb is actually implemented.
*/
if (ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE))
- return;
+ return -1;

set_cpu_cap(c, X86_FEATURE_XTOPOLOGY);

@@ -51,10 +49,30 @@ void detect_extended_topology(struct cpu
* initial apic id, which also represents 32-bit extended x2apic id.
*/
c->initial_apicid = edx;
+ smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
+#endif
+ return 0;
+}
+
+/*
+ * Check for extended topology enumeration cpuid leaf 0xb and if it
+ * exists, use it for populating initial_apicid and cpu topology
+ * detection.
+ */
+void detect_extended_topology(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_SMP
+ unsigned int eax, ebx, ecx, edx, sub_index;
+ unsigned int ht_mask_width, core_plus_mask_width;
+ unsigned int core_select_mask, core_level_siblings;
+
+ if (detect_extended_topology_early(c) < 0)
+ return;

/*
* Populate HT related information from sub-leaf level 0.
*/
+ cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);