Re: [PATCH 1/5] KVM: SVM: Drop stale comment from svm_hv_vmcb_dirty_nested_enlightenments()

Paolo Bonzini
2022-01-25T15:59:31Z

On 12/20/21 16:21, Vitaly Kuznetsov wrote:
> Commit 3fa5e8fd0a0e4 ("KVM: SVM: delay svm_vcpu_init_msrpm after
> svm->vmcb is initialized") re-arranged svm_vcpu_init_msrpm() call in
> svm_create_vcpu() making the comment about vmcb being NULL
> obsolete. Drop it.
>
> While on it, drop superfluous vmcb_is_clean() check: vmcb_mark_dirty()
> is a bit flip, an extra check is unlikely to bring any performance gain.
> Drop now-unneeded vmcb_is_clean() helper as well.
>
> Fixes: 3fa5e8fd0a0e4 ("KVM: SVM: delay svm_vcpu_init_msrpm after svm->vmcb is initialized")
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Queued, but with subject changed to "KVM: SVM: clean up beginning of
svm_hv_vmcb_dirty_nested_enlightenments()".

Paolo

> arch/x86/kvm/svm/svm.h | 5 -----
> arch/x86/kvm/svm/svm_onhyperv.h | 9 +--------
> 2 files changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index daa8ca84afcc..5d197aae3a19 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -305,11 +305,6 @@ static inline void vmcb_mark_all_clean(struct vmcb *vmcb)
> & ~VMCB_ALWAYS_DIRTY_MASK;
> }
>
> -static inline bool vmcb_is_clean(struct vmcb *vmcb, int bit)
> -{
> - return (vmcb->control.clean & (1 << bit));
> -}
> -
> static inline void vmcb_mark_dirty(struct vmcb *vmcb, int bit)
> {
> vmcb->control.clean &= ~(1 << bit);
> diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
> index c53b8bf8d013..cdbcfc63d171 100644
> --- a/arch/x86/kvm/svm/svm_onhyperv.h
> +++ b/arch/x86/kvm/svm/svm_onhyperv.h
> @@ -83,14 +83,7 @@ static inline void svm_hv_vmcb_dirty_nested_enlightenments(
> struct hv_enlightenments *hve =
> (struct hv_enlightenments *)vmcb->control.reserved_sw;
>
> - /*
> - * vmcb can be NULL if called during early vcpu init.
> - * And its okay not to mark vmcb dirty during vcpu init
> - * as we mark it dirty unconditionally towards end of vcpu
> - * init phase.
> - */
> - if (vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> - hve->hv_enlightenments_control.msr_bitmap)
> + if (hve->hv_enlightenments_control.msr_bitmap)
> vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
> }
>