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SubjectRe: [KVM timekeeping 13/35] Perform hardware_enable in CPU_STARTING callback
Zachary Amsden wrote:
> The CPU_STARTING callback was added upstream with the intention
> of being used for KVM, specifically for the hardware enablement
> that must be done before we can run in hardware virt. It had
> bugs on the x86_64 architecture at the time, where it was called
> after CPU_ONLINE. The arches have since merged and the bug is
> gone.

What bugs are you referring to, or since which kernel version is
CPU_STARTING usable for KVM? I need to encode this into kvm-kmod.

Thanks,
Jan

>
> It might be noted other features should probably start making
> use of this callback; microcode updates in particular which
> might be fixing important erratums would be best applied before
> beginning to run user tasks.
>
> Signed-off-by: Zachary Amsden <zamsden@redhat.com>
> ---
> virt/kvm/kvm_main.c | 5 ++---
> 1 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b78b794..d4853a5 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1958,10 +1958,10 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
> cpu);
> hardware_disable(NULL);
> break;
> - case CPU_ONLINE:
> + case CPU_STARTING:
> printk(KERN_INFO "kvm: enabling virtualization on CPU%d\n",
> cpu);
> - smp_call_function_single(cpu, hardware_enable, NULL, 1);
> + hardware_enable(NULL);
> break;
> }
> return NOTIFY_OK;
> @@ -2096,7 +2096,6 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>
> static struct notifier_block kvm_cpu_notifier = {
> .notifier_call = kvm_cpu_hotplug,
> - .priority = 20, /* must be > scheduler priority */
> };
>
> static int vm_stat_get(void *_offset, u64 *val)

--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux


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