Re: [Patch V5 13/16] xen: add explicit memblock_reserve() calls for special pages

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com,
	david.vrabel@citrix.com, boris.ostrovsky@oracle.com
Subject: Re: [Patch V5 13/16] xen: add explicit memblock_reserve() calls for special pages
Date: Fri, 10 Jul 2015 09:36:02 -0400	[thread overview]
Message-ID: <20150710133602.GH23038@l.oracle.com> (raw)
In-Reply-To: <1436532481-1224-14-git-send-email-jgross@suse.com>

> 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.

Is there an way to figure out whether these mfns are valid and just
piggyback on that?