| Subject: x86: kvm Require const tsc for RT |
| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Sun, 06 Nov 2011 12:26:18 +0100 |
| |
| Non constant TSC is a nightmare on bare metal already, but with |
| virtualization it becomes a complete disaster because the workarounds |
| are horrible latency wise. That's also a preliminary for running RT in |
| a guest on top of a RT host. |
| |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| --- |
| arch/x86/kvm/x86.c | 7 +++++++ |
| 1 file changed, 7 insertions(+) |
| |
| --- a/arch/x86/kvm/x86.c |
| +++ b/arch/x86/kvm/x86.c |
| @@ -6118,6 +6118,13 @@ int kvm_arch_init(void *opaque) |
| goto out; |
| } |
| |
| +#ifdef CONFIG_PREEMPT_RT_FULL |
| + if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { |
| + printk(KERN_ERR "RT requires X86_FEATURE_CONSTANT_TSC\n"); |
| + return -EOPNOTSUPP; |
| + } |
| +#endif |
| + |
| r = kvm_mmu_module_init(); |
| if (r) |
| goto out_free_percpu; |
