about: XENMEM_machphys_mfn_list

about: XENMEM_machphys_mfn_list

[Lin.Yu]

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Hi, all,

XENMEM_machphys_mfn_list command is used to acquire the mapping between the
pseudo-physical to machine. And the hypercall will fill in the struct
xen_machphys_mfn_list.

I do not understand "This table is an array of pseudo-physical frame numbers
of the start of 2MB extents, corresponding to 2MB rangs in the
pseudo-physical address space".
"This table" means the array pointed by xen_machphys_mfn_list.extent_start.

I am reading the code about this struct, still in confusion.
:-)
Who can help me?

-- 
Best Regards,
-- Lin.Yu

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Re: about: XENMEM_machphys_mfn_list

[BVK Chaitanya]

Lin.Yu wrote:
> 
> XENMEM_machphys_mfn_list command is used to acquire the mapping between 
> the pseudo-physical to machine. And the hypercall will fill in the 
> struct xen_machphys_mfn_list.
> 
> I do not understand "This table is an array of pseudo-physical frame 
> numbers of the start of 2MB extents, corresponding to 2MB rangs in the 
> pseudo-physical address space".
> "This table" means the array pointed by xen_machphys_mfn_list.extent_start.
> 
> I am reading the code about this struct, still in confusion.
> :-)
> Who can help me?
> 


AFAIU, here "table" is nothing more than an array of xen_pfn_ts.

Only complication is, mfns returned are `base-mfns' for 2MB memory regions.

For example, if mfn 100 is returned, it means mfns 100-612 hold the 2MB 
region (612 = 100 + 512; 512 pages make 2MB)


--
bvk-chaitanya

Re: about: XENMEM_machphys_mfn_list

[Lin.Yu]

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Got it.
But why 2MB? I have no any clue about it.

-- Lin
On Fri, Jul 18, 2008 at 5:10 PM, BVK Chaitanya <
bayapuneni_chaitanya@symantec.com> wrote:

> Lin.Yu wrote:
>
>>
>> XENMEM_machphys_mfn_list command is used to acquire the mapping between
>> the pseudo-physical to machine. And the hypercall will fill in the struct
>> xen_machphys_mfn_list.
>>
>> I do not understand "This table is an array of pseudo-physical frame
>> numbers of the start of 2MB extents, corresponding to 2MB rangs in the
>> pseudo-physical address space".
>> "This table" means the array pointed by
>> xen_machphys_mfn_list.extent_start.
>>
>> I am reading the code about this struct, still in confusion.
>> :-)
>> Who can help me?
>>
>>
>
> AFAIU, here "table" is nothing more than an array of xen_pfn_ts.
>
> Only complication is, mfns returned are `base-mfns' for 2MB memory regions.
>
> For example, if mfn 100 is returned, it means mfns 100-612 hold the 2MB
> region (612 = 100 + 512; 512 pages make 2MB)
>
>
> --
> bvk-chaitanya
>



-- 
Best Regards,
-- Lin.Yu

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