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From bc5cb37aa8e610d93aada2612abf77e85d034c75 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 6 Nov 2011 12:26:18 +0100
Subject: [PATCH 117/191] x86: kvm Require const tsc for RT
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 | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 47e021bdcc94..891c3239e2b0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7979,6 +7979,14 @@ int kvm_arch_init(void *opaque)
goto out;
}
+#ifdef CONFIG_PREEMPT_RT
+ if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
+ pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
+ r = -EOPNOTSUPP;
+ goto out;
+ }
+#endif
+
r = -ENOMEM;
x86_fpu_cache = kmem_cache_create("x86_fpu", sizeof(struct fpu),
__alignof__(struct fpu), SLAB_ACCOUNT,
--
2.19.1
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