On Tue, May 22, 2018 at 09:54:20AM -0700, Jim Mattson wrote:
> Previously, we only called indirect_branch_prediction_barrier on the
> logical CPU that freed a vmcb. This function should be called on all
> logical CPUs that last loaded the vmcb in question.
>
> Fixes: 15d45071523d ("KVM/x86: Add IBPB support")
> Reported-by: Neel Natu <neelnatu@xxxxxxxxxx>
> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Thank you!
> ---
> arch/x86/kvm/svm.c | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 220e5a89465a..ffa27f75e323 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2172,21 +2172,31 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
> return ERR_PTR(err);
> }
>
> +static void svm_clear_current_vmcb(struct vmcb *vmcb)
> +{
> + int i;
> +
> + for_each_online_cpu(i)
> + cmpxchg(&per_cpu(svm_data, i)->current_vmcb, vmcb, NULL);
> +}
> +
> static void svm_free_vcpu(struct kvm_vcpu *vcpu)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> + /*
> + * The vmcb page can be recycled, causing a false negative in
> + * svm_vcpu_load(). So, ensure that no logical CPU has this
> + * vmcb page recorded as its current vmcb.
> + */
> + svm_clear_current_vmcb(svm->vmcb);
> +
> __free_page(pfn_to_page(__sme_clr(svm->vmcb_pa) >> PAGE_SHIFT));
> __free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
> __free_page(virt_to_page(svm->nested.hsave));
> __free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER);
> kvm_vcpu_uninit(vcpu);
> kmem_cache_free(kvm_vcpu_cache, svm);
> - /*
> - * The vmcb page can be recycled, causing a false negative in
> - * svm_vcpu_load(). So do a full IBPB now.
> - */
> - indirect_branch_prediction_barrier();
> }
>
> static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> --
> 2.17.0.441.gb46fe60e1d-goog
>
