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From 53f33d36d7741754ec7b7f2e4a0c62faa30d6902 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sun, 6 Nov 2011 12:26:18 +0100
Subject: [PATCH 090/347] x86: kvm Require const tsc for RT
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz
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(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 417abc9ba1ad..9829e0fbdd41 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6875,6 +6875,13 @@ 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;
--
2.36.1
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