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kvm: x86: Require const tsc for RT

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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>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Message-Id: <Yh5eJSG19S2sjZfy@linutronix.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Thomas Gleixner 2011-11-06 12:26:18 +01:00 committed by Paolo Bonzini
parent f144c49e8c
commit 5e17b2ee45
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kvm/x86.c
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@ -8865,6 +8865,12 @@ int kvm_arch_init(void *opaque)
goto out;
}
if (IS_ENABLED(CONFIG_PREEMPT_RT) && !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
r = -EOPNOTSUPP;
goto out;
}
r = -ENOMEM;
x86_emulator_cache = kvm_alloc_emulator_cache();