Re: [PATCH v2] KVM: x86: zero kvmclock_offset when vcpu0 initializes kvmclock system MSR

From: Luiz Capitulino
Date: Tue May 26 2015 - 09:22:55 EST


On Sat, 23 May 2015 17:06:29 -0300
Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote:

> Initialize kvmclock base, on kvmclock system MSR write time,
> so that the guest sees kvmclock counting from zero.
>
> This matches baremetal behaviour when kvmclock in guest
> sets sched clock stable.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

Tested-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx>

>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cc2c759..ea40d24 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2188,6 +2188,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> &vcpu->requests);
>
> ka->boot_vcpu_runs_old_kvmclock = tmp;
> +
> + ka->kvmclock_offset = -get_kernel_ns();
> }
>
> vcpu->arch.time = data;
> --
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