Re: [PATCH 0/2] xen: modify dom0 interface for obtaining memory map

[Juergen Gross <jgross@suse.com>]

On 05/12/16 17:39, Andrew Cooper wrote:
> On 05/12/16 16:34, Juergen Gross wrote:
>> Today's interface to get the machine memory map in dom0 requires to
>> know in advance how large the final map will be. There is however no
>> way to either get only a part of the memory map or to ask the
>> hypervisor about its size.
>>
>> This patch set enhances the XENMEM_machine_memory_map hypercall to
>> solve both issues by returning only a partial memory map in case the
>> supplied buffer was too small and to return the needed number of
>> entries if no buffer is being supplied.
> 
> These changes appear to be a good improvement in behaviour.
> 
> However, there is a way to know the exact size of the memory map.  Use
> XENMEM_maximum_ram_page to find the maximum mfn, and use that to
> calculate the size of the mapping.
> 
> See tools/libxc/xc_sr_common_x86_pv.c: x86_pv_map_m2p()

How does this help for the size of the E820 map of the physical machine
"enhanced" by the hypervisor to reflect holes for IOAPICs and IOMMU?

The problem is related to the *machine* memory map!


Juergen


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