x86/cpu/AMD: Evaluate smp_num_siblings early

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

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Orabug: 28220674
CVE: CVE-2018-3620

(cherry picked from commit 1e1d7e25fd759eddf96d8ab39d0a90a1979b2d8c)

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/amd.c
Contextual

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index eaa846fa27335497e19d374e1075348fbf7a2e95..199809d443a83a99f830531259179393ab90257c 100644 (file)
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -283,6 +283,16 @@ static int nearby_node(int apicid)
 }
 #endif
 
+static void amd_get_topology_early(struct cpuinfo_x86 *c)
+{
+       if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
+               u32 eax, ebx, ecx, edx;
+
+               cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
+               smp_num_siblings = ((ebx >> 8) & 0xff) + 1;
+       }
+}
+
 /*
  * Fixup core topology information for
  * (1) AMD multi-node processors
@@ -560,6 +570,8 @@ static void early_init_amd(struct cpuinfo_x86 *c)
        /* F16h erratum 793, CVE-2013-6885 */
        if (c->x86 == 0x16 && c->x86_model <= 0xf)
                msr_set_bit(MSR_AMD64_LS_CFG, 15);
+
+       amd_get_topology_early(c);
 }
 
 static const int amd_erratum_383[];