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-rw-r--r--debian/patches-rt/0212-x86-kvm-Require-const-tsc-for-RT.patch38
1 files changed, 38 insertions, 0 deletions
diff --git a/debian/patches-rt/0212-x86-kvm-Require-const-tsc-for-RT.patch b/debian/patches-rt/0212-x86-kvm-Require-const-tsc-for-RT.patch
new file mode 100644
index 000000000..461bb6d81
--- /dev/null
+++ b/debian/patches-rt/0212-x86-kvm-Require-const-tsc-for-RT.patch
@@ -0,0 +1,38 @@
+From 6ef3a23d8f37d55fa94b9f1212830a3b8018c76f Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Sun, 6 Nov 2011 12:26:18 +0100
+Subject: [PATCH 212/323] x86: kvm Require const tsc for RT
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.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 | 8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
+index 13e4699a0744..21a1aa76eb23 100644
+--- a/arch/x86/kvm/x86.c
++++ b/arch/x86/kvm/x86.c
+@@ -8167,6 +8167,14 @@ 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,
+--
+2.43.0
+