Re: [PATCH v2 1/5] vmx: Refactor vpid_sync_vcpu_gva()

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

Le 10/09/2026 à 17:45, Jan Beulich a écrit :
> On 31.07.2026 16:46, Teddy Astie wrote:
> > --- a/xen/arch/x86/include/asm/hvm/vmx/vmx.h
> > +++ b/xen/arch/x86/include/asm/hvm/vmx/vmx.h
> > @@ -460,19 +460,16 @@ static inline void vpid_sync_vcpu_gva(struct vcpu *v, 
> > unsigned long gva)
> >        * If individual address invalidation is not supported, we escalate to
> >        * use single context invalidation.
> >        */
> > -    if ( likely(cpu_has_vmx_vpid_invvpid_individual_addr) )
> > -        goto execute_invvpid;
> > -
> > -    type = INVVPID_SINGLE_CONTEXT;
> > +    if ( unlikely(!cpu_has_vmx_vpid_invvpid_individual_addr) )
> > +        type = INVVPID_SINGLE_CONTEXT;
> >   
> >       /*
> >        * If single context invalidation is not supported, we escalate to
> >        * use all context invalidation.
> >        */
> > -    if ( !cpu_has_vmx_vpid_invvpid_single_context )
> > +    if ( unlikely(!cpu_has_vmx_vpid_invvpid_single_context) )
> >           type = INVVPID_ALL_CONTEXT;
> >   
> > -execute_invvpid:
> >       __invvpid(type, v->arch.hvm.n1asid.asid, (u64)gva);
> >   }
> But this isn't functionally identical to the original, at least in the
> cpu_has_vmx_vpid_invvpid_individual_addr &&
> !cpu_has_vmx_vpid_invvpid_single_context case. We'd now end up using
> INVVPID_ALL_CONTEXT there, when it wants to continue to be
> INVVPID_INDIVIDUAL_ADDR.
Yes, though a good question is to know if there exist a CPU that has 
INVVPID_INDIVIDUAL_ADDR without INVVPID_SINGLE_CONTEXT; otherwise, we 
can just say that this is not supposed to happen.
One alternative I have in mind would be to have cascading fallbacks to 
"larger scope" alternatives.
i.e

static inline void vpid_sync_all(void)
{
    __invvpid(INVVPID_ALL_CONTEXT, 0, 0);
}

static inline void vpid_sync_vcpu_context(const struct vcpu *v)
{
    /*
     * If single context invalidation is not supported, we escalate to
     * use all context invalidation.
     */
    if ( unlikely(!cpu_has_vmx_vpid_invvpid_single_context) )
        return vpid_sync_all();

    __invvpid(INVVPID_SINGLE_CONTEXT, v->arch.hvm.n1asid.asid, 0);
}

static inline void vpid_sync_vcpu_gva(struct vcpu *v, unsigned long gva)
{
    /*
     * If individual address invalidation is not supported, we escalate to
     * use single context invalidation.
     */
    if ( unlikely(!cpu_has_vmx_vpid_invvpid_individual_addr) )
        return vpid_sync_vcpu_context(v);

    __invvpid(INVVPID_INDIVIDUAL_ADDR, v->arch.hvm.n1asid.asid, (u64)gva);
}

That requires introducing vpid_sync_vcpu_context() ahead, but would 
avoid the corner case without making things too complex.
> Jan
Teddy

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