Re: [Xen-devel] [PATCH RESEND v5 2/6] xen/arm: Implement get_maximum_gpfn hypercall for arm

[Eugene Fedotov <e.fedotov@xxxxxxxxxxx>]

15.11.2013 11:04, Eugene Fedotov wrote:
> 13.11.2013 14:58, Ian Campbell  wrote:
> > On Wed, 2013-11-13 at 12:28 +0400, Eugene Fedotov wrote:
> > > > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> > > > > index 123280e..3801f07 100644
> > > > > --- a/xen/arch/arm/mm.c
> > > > > +++ b/xen/arch/arm/mm.c
> > > > > @@ -927,7 +927,11 @@ int page_is_ram_type(unsigned long mfn, 
> > > > > unsigned long mem_type)
> > > > >       unsigned long domain_get_maximum_gpfn(struct domain *d)
> > > > s/unsigned long/xen_pfn_t/ I think.
> > > >
> > > > Urk, which will break the ABI for this hypercall. That's something 
> > > > of a
> > > > conundrum :-/
> > > >
> > > > It is a domctl so we are at liberty to change it, probably to taking a
> > > > xen_pfn_t * to fill in instead of returning the value.
> > > >
> > > > I'm in two minds about whether we should do so now or postpone it 
> > > > (which
> > > > risks forgetting and having an obscure bug somewhere down the line).
> > > OK, this way, or other solution is to purge this hypercall yet in
> > > migration and use max_memkb field in DOMCTL_getdomaininfo to obtain the
> > > maximum PFN.
> > Is there an interface to retrieve that? I don't see it :-( 
No, it is another hypercall XEN_DOMCTL_getdomaininfo. max_memkb field in 
xc_dominfo_t structure is a second way to retrieve maximum memory size 
and calculate PFN. Do we need domain_get_maximum_gpfn ?
In addition to this question I need to ask why we need xen_pfn_t (that 
is always 64 bit on Xen-arm) for physical memory PFN. Currently the 
following libxc proxies for DOMCTL:
xc_domain_setmaxmem and max_memkb field in xc_domain_getinfo()  are 
working with unsigned long max_mem_kb parameter (that is 32 bit for ARM32)
In case if 64 bit PFN is needed, xen_pfn_t returning hypercall looks 
like better then xc_domain_getinfo() .
Best regards,
Evgeny.


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