linux-kernel - Re: [Xen-devel] [PATCH 02/13] xen: anchor linear p2m list in shared info structure

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Date:	Wed, 18 Feb 2015 10:32:19 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<david.vrabel@...rix.com>, <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH 02/13] xen: anchor linear p2m list in shared
 info structure

On 18/02/15 06:51, Juergen Gross wrote:
> The linear p2m list should be anchored in the shared info structure

I'm not really sure what you mean by "anchored".

> read by the Xen tools to be able to support 64 bit pv-domains larger
> than 512 MB. Additionally the linear p2m list interface includes a
> generation count which is changed prior to and after each mapping
> change of the p2m list. Reading the generation count the Xen tools can
> detect changes of the mappings and re-read the p2m list eventually.
[...]
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -256,6 +256,10 @@ void xen_setup_mfn_list_list(void)
>  	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
>  		virt_to_mfn(p2m_top_mfn);
>  	HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
> +	HYPERVISOR_shared_info->arch.p2m_generation = 0;
> +	HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
> +	HYPERVISOR_shared_info->arch.p2m_cr3 =
> +		xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
>  }
>  
>  /* Set up p2m_top to point to the domain-builder provided p2m pages */
> @@ -469,8 +473,10 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
>  
>  		ptechk = lookup_address(vaddr, &level);
>  		if (ptechk == pte_pg) {
> +			HYPERVISOR_shared_info->arch.p2m_generation++;
>  			set_pmd(pmdp,
>  				__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
> +			HYPERVISOR_shared_info->arch.p2m_generation++;

Do these increments of p2m_generation need to be atomic?

David
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