Re: [Xen-devel] [PATCH v2 06/10] x86/SVM: Add AVIC vmexit handlers

[Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>]

Hi Boris,

On 1/3/17 22:34, Boris Ostrovsky wrote:
> > +static int avic_handle_dfr_update(struct vcpu *v)
> > +{
> > +    u32 mod;
> > +    struct svm_domain *d = &v->domain->arch.hvm_domain.svm;
> > +    u32 *dfr = avic_get_bk_page_entry(v, APIC_DFR);
> > +
> > +    if ( !dfr )
> > +        return -EINVAL;
> > +
> > +    mod = (*dfr >> 28) & 0xFu;
> > +
> > +    spin_lock(&d->avic_ldr_mode_lock);
> > +    if ( d->avic_ldr_mode != mod )
> > +    {
> > +        /*
> > +         * We assume that all local APICs are using the same type.
> > +         * If LDR mode changes, we need to flush the domain AVIC logical
> > +         * APIC id table.
> > +         */
> > +        clear_domain_page(_mfn(d->avic_log_apic_id_table_mfn));
> > +        smp_wmb();
> Is this needed? I think clear_page() guarantees visibility/ordering (we
> have SFENCE in clear_page_sse2() for this reason).
>
> -boris
Ah... Okay. Thanks for pointing out.

Suravee

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