Hi Gerd,
On Wed, Feb 04, 2009 at 05:52:04PM +0100, Gerd Hoffmann wrote:
> kvmclock currently falls apart on machines without constant tsc.
> This patch fixes it. Changes:
>
> * keep tsc frequency in a per-cpu variable.
> * handle kvmclock update using a new request flag, thus checking
> whenever we need an update each time we enter guest context.
> * use a cpufreq notifier to track frequency changes and force
> kvmclock updates.
> * send ipis to kick cpu out of guest context if needed to make
> sure the guest doesn't see stale values.
>
> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 99 +++++++++++++++++++++++++++++++++++++++++++---
> include/linux/kvm_host.h | 1 +
> 2 files changed, 94 insertions(+), 6 deletions(-)
>
> + spin_lock(&kvm_lock);
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + for (i = 0; i < KVM_MAX_VCPUS; ++i) {
> + vcpu = kvm->vcpus[i];
> + if (!vcpu)
> + continue;
> + if (vcpu->cpu != freq->cpu)
> + continue;
> + if (!kvm_request_guest_time_update(vcpu))
> + continue;
> + if (vcpu->cpu != smp_processor_id())
> + send_ipi++;
> + }
> + }
> + spin_unlock(&kvm_lock);
The loop is cold hearted, but Juan's cleanups can be worked for 2.6.30
merge window. Given how many people have hit the bug better have
something non invasive until then.
> +
> + if (freq->old < freq->new && send_ipi) {
Can you fix the whitespace breakage please?
> + smp_call_function_single(freq->cpu, bounce_off, NULL, 1);
> + }
> + return 0;
> +}
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