Re: [Xen-devel] [PATCH 2/6] xc: use XENMEM_claim_pages during guest creation.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-03-13 at 14:42 +0000, Konrad Rzeszutek Wilk wrote:
> > > @@ -506,10 +517,16 @@ static int setup_guest(xc_interface *xch,
> > >          munmap(page0, PAGE_SIZE);
> > >      }
> > >  
> > > +    /* ensure no unclaimed pages are left unused */
> > > +    xc_domain_claim_pages(xch, dom, 0 /* cancels the claim */);
> > 
> > This cannot fail?
> 
> It can (say we use an older hypervisor that does not have this subop), in
> which case any of the operations would return -ENOSYS - which is OK.

Right, that's seems ok

> But in case of the hypervisor having this implemented - yes - this call
> should not fail.
> 
> Thought I should probably redo the first call to be more like:
> 
>  if (claim_mode) {
> 
>       rc =..
>       if ( rc == -ENOSYS)
>               rc = 0; // Whatever, hypervisor is out sync.
>       if ( rc != 0 )

If I follow correctly then yes, I think that would be better.

I wonder if
+ PERROR("Could not allocate memory for HVM guest.");
and friends ought to say "claim" to distinguish from a later failure to
allocate memory?

Ian.


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