Re: [XenPPC][Patch 2/3] xen patches for xm save/restore

[geyi <kudva@xxxxxxxxxxxxxx>]

Hollis Blanchard wrote:
> On Thu, 2006-11-02 at 11:49 -0500, geyi wrote:
> > +    case XEN_DOMCTL_getshadowlist:
> > +    {
> > +       struct domain *d = find_domain_by_id(domctl->domain);
> > +       uint num_ptes;
> > +
> > +       printk(" XEN_DOMCTL_getshadowlist: \n");
> > +
> > +       ret = -EINVAL;
> > +       if ( d != NULL)
> > +       {
> > +          ret = 0;
> > +
> > +          domctl->u.getshadowlist.htab_map = (uint64_t)(d->arch.htab.map);
> > +          printk("htab_map: 0x%016lx\n",(uint64_t)(d->arch.htab.map));
> > +
> > +          num_ptes = 1UL << d->arch.htab.log_num_ptes;
> > +          domctl->u.getshadowlist.htab_num_ptes = num_ptes; 
> Here you've set htab_map to a machine address. What is the domain
> supposed to do with that? Does "save" destroy the domain? Are you
> expecting that address to be valid once the domain is destroyed?
>
> The operation is called "getshadowlist", but there is no list here.
> Wouldn't a copying a list into a domain-provided buffer make more sense?
The htab for a domain is not so small to copy it to the user space in 
one hcall. For a 64MB domain, the size of htab  is 1MB(256 pages), and 
it grows when the domain becomes bigger. This hcall return the start 
point of the htab array to application. So user can access the shadow 
list page by page.
Now this hcall is used only in domain save/restore scenario. The save 
process reads the shadow list, converts the mfn of each valid entry to 
pfn and save them to the file. After all things done, the saved domain 
will be destroyed. On the restore side, the machine address of new 
domain shadow list will be given with this call. The pte entries stored 
in file will be copied back to it, after the pfn in the entries is 
converted back to mfn. So the machine address of shadow list will be 
only used when domain is valid.
--
Yi Ge <kudva@xxxxxxxxxxxxxx>


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