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SubjectRe: [Patch V5 13/16] xen: add explicit memblock_reserve() calls for special pages
On Mon, Jul 13, 2015 at 06:10:23AM +0200, Juergen Gross wrote:
> On 07/10/2015 03:36 PM, Konrad Rzeszutek Wilk wrote:
> >>diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> >>index 1982617..c28f7f7 100644
> >>--- a/arch/x86/xen/mmu.c
> >>+++ b/arch/x86/xen/mmu.c
> >>@@ -2084,6 +2084,19 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
> >> }
> >> #endif /* CONFIG_X86_64 */
> >>
> >>+void __init xen_reserve_special_pages(void)
> >>+{
> >>+ phys_addr_t paddr;
> >>+
> >>+ memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
> >>+ if (!xen_initial_domain()) {
> >>+ paddr = PFN_PHYS(mfn_to_pfn(xen_start_info->store_mfn));
> >>+ memblock_reserve(paddr, PAGE_SIZE);
> >>+ paddr = PFN_PHYS(mfn_to_pfn(xen_start_info->console.domU.mfn));
> >>+ memblock_reserve(paddr, PAGE_SIZE);
> >>+ }
> >
> >I believe we can start an MiniOS as the 'dom0' (so first domain), and then
> >Linux right after as the 'dom1' (semi-dom0?). In which case XenStore would
> >be actually available.
>
> And this dom1 would still be the "initial domain" (SIF_INITDOMAIN set)?

Yes.
>
> I couldn't spot other Xen usage of this flag as the one in the
> hypervisor when constructing the "real" initial domain.
>
> >Is there an way to figure out whether these mfns are valid and just
> >piggyback on that?
>
> For store_mfn: yes (it's initialized to 0 by the hypervisor).

Excellent. Lets at least piggyback on that.
>
> The console mfn: no, as the console info is a union which will hold
> different information in case of the initial domain.

OK.
>
>
> Juergen


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