On Fri, Jul 20, 2012 at 10:50:11AM -0600, Bruce Rogers wrote:
> When a guest is migrated, a time offset is generated in order to
> maintain the correct kvmclock based time for the guest. Detect when
> all kvmclock time pages are deleted so that the kvmclock offset can
> be safely reset to zero.
>
> Cc: Glauber Costa <glommer@xxxxxxxxxx>
> Cc: Zachary Amsden <zamsden@xxxxxxxxx>
> Signed-off-by: Bruce Rogers <brogers@xxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/x86.c | 5 ++++-
> 2 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index db7c1f2..112415c 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -524,6 +524,7 @@ struct kvm_arch {
>
> unsigned long irq_sources_bitmap;
> s64 kvmclock_offset;
> + unsigned int n_time_pages;
> raw_spinlock_t tsc_write_lock;
> u64 last_tsc_nsec;
> u64 last_tsc_write;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 14c290d..350c51b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1511,6 +1511,8 @@ static void kvmclock_reset(struct kvm_vcpu *vcpu)
> if (vcpu->arch.time_page) {
> kvm_release_page_dirty(vcpu->arch.time_page);
> vcpu->arch.time_page = NULL;
> + if (--vcpu->kvm->arch.n_time_pages == 0)
> + vcpu->kvm->arch.kvmclock_offset = 0;
> }
> }
>
> @@ -1624,7 +1626,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
> if (is_error_page(vcpu->arch.time_page)) {
> kvm_release_page_clean(vcpu->arch.time_page);
> vcpu->arch.time_page = NULL;
> - }
> + } else
> + vcpu->kvm->arch.n_time_pages++;
> break;
> }
> case MSR_KVM_ASYNC_PF_EN:
Userspace is responsible for configuring a correct kvmclock_offset
AFAICS?
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