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| author | Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> | 2018-06-20 11:29:53 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-07-04 20:49:38 +0200 |
| commit | 26acfb666a473d960f0fd971fe68f3e3ad16c70b (patch) | |
| tree | e534e6f16c22dc327c0159ecff72d68b1119ac8a /arch/x86/kvm | |
| parent | 0cc3cd21657be04cb0559fe8063f2130493f92cf (diff) | |
| download | linux-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 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/vmx.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 559a12b6184d..f2e7b6d016c9 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -71,6 +71,9 @@ static const struct x86_cpu_id vmx_cpu_id[] = { }; MODULE_DEVICE_TABLE(x86cpu, vmx_cpu_id); +static bool __read_mostly nosmt; +module_param(nosmt, bool, S_IRUGO); + static bool __read_mostly enable_vpid = 1; module_param_named(vpid, enable_vpid, bool, 0444); @@ -10370,10 +10373,20 @@ free_vcpu: return ERR_PTR(err); } +#define L1TF_MSG "SMT enabled with L1TF CPU bug present. Refer to CVE-2018-3620 for details.\n" + static int vmx_vm_init(struct kvm *kvm) { if (!ple_gap) kvm->arch.pause_in_guest = true; + + if (boot_cpu_has(X86_BUG_L1TF) && cpu_smt_control == CPU_SMT_ENABLED) { + if (nosmt) { + pr_err(L1TF_MSG); + return -EOPNOTSUPP; + } + pr_warn(L1TF_MSG); + } return 0; } |