Subject: x86: kvm Require const tsc for RT From: Thomas Gleixner Date: Sun Nov 6 12:26:18 2011 +0100 Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.16/older/patches-5.16-rc2-rt4.tar.xz From: Thomas Gleixner 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 --- arch/x86/kvm/x86.c | 6 ++++++ 1 file changed, 6 insertions(+) --- --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8605,6 +8605,12 @@ 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();