Hi Yamahata-san,
Thanks to point out.
I'll take care for SMP-safe from now on.
Actually vcpu_itc_no_srlz() in ia64_map_hypercall_param() is called
only when a guest requests __HYPERVISOR_grant_table_op. I think the
race condition can hardly occur.
So I'd prefer to wait for xencomm rather than fix it now.
Thanks,
Kouya
Isaku Yamahata writes:
> Hi.
>
> Sorry for delayed point out.
> At first I thought your hack would be replaced with xencomm.
> However it seems to take a while to merge xencomm for IA64 so that
> I decided to point it out now.
>
>
> On Fri, Aug 11, 2006 at 07:01:10PM +0900, Kouya SHIMURA wrote:
> Content-Description: message body text
> > diff -r fc6c3d866477 xen/arch/ia64/xen/vcpu.c
> > --- a/xen/arch/ia64/xen/vcpu.c Wed Aug 09 10:32:23 2006 -0600
> > +++ b/xen/arch/ia64/xen/vcpu.c Fri Aug 11 18:35:31 2006 +0900
> > @@ -2215,3 +2215,27 @@ IA64FAULT vcpu_ptr_i(VCPU *vcpu,UINT64 v
> >
> > return IA64_NO_FAULT;
> > }
> > +
> > +int ia64_map_hypercall_param(void)
> > +{
> > + struct vcpu *v = current;
> > + struct domain *d = current->domain;
> > + u64 vaddr = v->arch.hypercall_param.va & PAGE_MASK;
> > + volatile pte_t* pte;
> > +
> > + if (v->arch.hypercall_param.va == 0)
> > + return FALSE;
> > + pte = lookup_noalloc_domain_pte(d, v->arch.hypercall_param.pa1);
> > + if (!pte || !pte_present(*pte))
> > + return FALSE;
> > + vcpu_itc_no_srlz(v, 2, vaddr, pte_val(*pte), -1UL, PAGE_SHIFT);
> > + if (v->arch.hypercall_param.pa2) {
> > + vaddr += PAGE_SIZE;
> > + pte = lookup_noalloc_domain_pte(d, v->arch.hypercall_param.pa2);
> > + if (pte && pte_present(*pte)) {
> > + vcpu_itc_no_srlz(v, 2, vaddr, pte_val(*pte), -1UL,
> > PAGE_SHIFT);
> > + }
> > + }
> > + ia64_srlz_d();
> > + return TRUE;
> > +}
>
>
> This isn't SMP-safe. Since the p2m table is locklesss,
> another vcpu might change the p2m table entry after checking pte_present()
> but before vcpu_itc_no_srlz(). You must be aware of it.
>
> --
> yamahata
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