From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tim Deegan <tim@xen.org>
Subject: Re: [RFC][PATCH 02/13] introduce
	XENMEM_reserved_device_memory_map
Date: Thu, 16 Apr 2015 15:59:16 +0100
Message-ID: <20150416145916.GF13441@deinos.phlegethon.org>
References: <1428657724-3498-1-git-send-email-tiejun.chen@intel.com>
	<1428657724-3498-3-git-send-email-tiejun.chen@intel.com>
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To: Tiejun Chen <tiejun.chen@intel.com>
Cc: kevin.tian@intel.com, wei.liu2@citrix.com, ian.campbell@citrix.com, andrew.cooper3@citrix.com, Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org, stefano.stabellini@citrix.com, JBeulich@suse.com, yang.z.zhang@intel.com
List-Id: xen-devel@lists.xenproject.org

Hi,

At 17:21 +0800 on 10 Apr (1428686513), Tiejun Chen wrote:
> diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
> index 2b5206b..36e5f54 100644
> --- a/xen/include/public/memory.h
> +++ b/xen/include/public/memory.h
> @@ -574,7 +574,37 @@ struct xen_vnuma_topology_info {
>  typedef struct xen_vnuma_topology_info xen_vnuma_topology_info_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_vnuma_topology_info_t);
>  
> -/* Next available subop number is 27 */
> +/*
> + * For legacy reasons, some devices must be configured with special memory
> + * regions to function correctly.  The guest would take these regions
> + * according to different user policies.
> + */

I don't understand what this means.  Can you try to write a comment
that would tell an OS developer:
 - what the reserved device memory map actually means; and
 - what this hypercall does.

> @@ -121,6 +121,8 @@ void iommu_dt_domain_destroy(struct domain *d);
>  
>  struct page_info;
>  
> +typedef int iommu_grdm_t(xen_pfn_t start, xen_ulong_t nr, u32 id, void *ctxt);

This needs a comment describing what the return values are.

Cheers,

Tim.