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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2018-06-20 11:29:53 -0400
committerThomas Gleixner <tglx@linutronix.de>2018-07-04 20:49:38 +0200
commit26acfb666a473d960f0fd971fe68f3e3ad16c70b (patch)
treee534e6f16c22dc327c0159ecff72d68b1119ac8a /kernel/cpu.c
parent0cc3cd21657be04cb0559fe8063f2130493f92cf (diff)
downloadlinux-26acfb666a473d960f0fd971fe68f3e3ad16c70b.tar.bz2
x86/KVM: Warn user if KVM is loaded SMT and L1TF CPU bug being present
If the L1TF CPU bug is present we allow the KVM module to be loaded as the major of users that use Linux and KVM have trusted guests and do not want a broken setup. Cloud vendors are the ones that are uncomfortable with CVE 2018-3620 and as such they are the ones that should set nosmt to one. Setting 'nosmt' means that the system administrator also needs to disable SMT (Hyper-threading) in the BIOS, or via the 'nosmt' command line parameter, or via the /sys/devices/system/cpu/smt/control. See commit 05736e4ac13c ("cpu/hotplug: Provide knobs to control SMT"). Other mitigations are to use task affinity, cpu sets, interrupt binding, etc - anything to make sure that _only_ the same guests vCPUs are running on sibling threads. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/cpu.c')
-rw-r--r--kernel/cpu.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6f3a3cde8b83..5a00ebdf98c6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -345,6 +345,7 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
#ifdef CONFIG_HOTPLUG_SMT
enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
+EXPORT_SYMBOL_GPL(cpu_smt_control);
static int __init smt_cmdline_disable(char *str)
{