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kvm: x86: Limit the number of "kvm: disabled by bios" messages

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In older version of systemd(219), at boot time, udevadm is called with :
	/usr/bin/udevadm trigger --type=devices --action=add"

This program generates an echo "add" in /sys/devices/system/cpu/cpu<x>/uevent,
leading to the "kvm: disabled by bios" message in case of your Bios disabled
the virtualization extensions.

On a modern system running up to 256 CPU threads, this pollutes the Kernel logs.

This patch offers to ratelimit this message to avoid any userspace program triggering
this uevent printing this message too often.

This patch is only a workaround but greatly reduce the pollution without
breaking the current behavior of printing a message if some try to instantiate
KVM on a system that doesn't support it.

Note that recent versions of systemd (>239) do not have trigger this behavior.

This patch will be useful at least for some using older systemd with recent Kernels.

Signed-off-by: Erwan Velu <e.velu@criteo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Erwan Velu 2020-02-27 19:00:46 +01:00 committed by Paolo Bonzini
parent aaec7c03de
commit ef935c25fd
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kvm/x86.c
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@ -7308,12 +7308,12 @@ int kvm_arch_init(void *opaque)
}
if (!ops->cpu_has_kvm_support()) {
printk(KERN_ERR "kvm: no hardware support\n");
pr_err_ratelimited("kvm: no hardware support\n");
r = -EOPNOTSUPP;
goto out;
}
if (ops->disabled_by_bios()) {
printk(KERN_ERR "kvm: disabled by bios\n");
pr_err_ratelimited("kvm: disabled by bios\n");
r = -EOPNOTSUPP;
goto out;
}