From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 5 Jun 2018 22:53:57 +0000 (+0200)
Subject: x86/cpu/common: Provide detect_ht_early()
X-Git-Tag: v4.1.12-124.31.3~655
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=7b32a4c42e9f8346bf5802edd2257134b5ff1b2e;p=users%2Fjedix%2Flinux-maple.git

x86/cpu/common: Provide detect_ht_early()

To support force disabling of SMT it's required to know the number of
thread siblings early. detect_ht() 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@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>

Orabug: 28220674
CVE: CVE-2018-3620

(cherry picked from commit 545401f4448a807b963ff17b575e0a393e68b523)

Signed-off-by: Mihai Carabas <mihai.carabas@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Conflicts:
	arch/x86/kernel/cpu/common.c
	arch/x86/kernel/cpu/cpu.h
Contextual
---

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 82af675cd3b4..598c2a9cc149 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -574,32 +574,36 @@ static void cpu_detect_tlb(struct cpuinfo_x86 *c)
 		tlb_lld_4m[ENTRIES], tlb_lld_1g[ENTRIES]);
 }
 
-void detect_ht(struct cpuinfo_x86 *c)
+int detect_ht_early(struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_X86_HT
 	u32 eax, ebx, ecx, edx;
-	int index_msb, core_bits;
 
 	if (!cpu_has(c, X86_FEATURE_HT))
-		return;
+		return -1;
 
 	if (cpu_has(c, X86_FEATURE_CMP_LEGACY))
-		return;
+		return -1;
 
 	if (cpu_has(c, X86_FEATURE_XTOPOLOGY))
-		return;
+		return -1;
 
 	cpuid(1, &eax, &ebx, &ecx, &edx);
 
 	smp_num_siblings = (ebx & 0xff0000) >> 16;
+	if (smp_num_siblings == 1)
+		pr_info_once("CPU0: Hyper-Threading is disabled\n");
+#endif
+	return 0;
+}
 
-	if (!smp_num_siblings)
-		smp_num_siblings = 1;
+void detect_ht(struct cpuinfo_x86 *c)
+{
+#ifdef CONFIG_X86_HT
+	int index_msb, core_bits;
 
-	if (smp_num_siblings == 1) {
-		printk_once(KERN_INFO "CPU0: Hyper-Threading is disabled\n");
+	if (detect_ht_early(c) < 0)
 		return;
-	}
 
 	index_msb = get_count_order(smp_num_siblings);
 	c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid, index_msb);
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index 5a9a5d6538b7..aff12c9cd277 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -46,6 +46,7 @@ extern const struct cpu_dev *const __x86_cpu_dev_start[],
 extern void get_cpu_cap(struct cpuinfo_x86 *c,
 			enum get_cpu_cap_behavior behavior);
 extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
+extern int detect_ht_early(struct cpuinfo_x86 *c);
 extern void x86_spec_ctrl_setup_ap(void);
 
 #endif /* ARCH_X86_CPU_H */