On 03/12/13 13:48, Yunbin Wang wrote:> Hi Andrew,
> Thanks for your reply.
>
> How does Xen map guest virtual address to machine physical address in
> PV mode?
>
> In PV mode, guests are aware of VMM, and know the actual physical
> memory address assigned to them, so do they map guest virtual address
> to guest physical address first, and then map physical address to
> machine physical, OR they map virtual address to machine physical
> directly?
>
> Thanks,
> Yunbin Wang
Please do not drop xen-devel from CC, and please do not top-post.
Xen does not keep track of guest virtual address - that is the guests
job to do. Xen maintains the pagetables, but the PV guest has to ask
Xen to update a PTE, and what value to update it to.
PV guests are aware that their physical address space is not contiguous,
and have to take this into account for memory management purposes.
~Andrew
>
>
> 2013/11/18 Andrew Cooper <andrew.cooper3@citrix.com
> <mailto:andrew.cooper3@citrix.com>>
>
> On 17/11/13 00:26, Yunbin Wang wrote:
>> Hi all,
>> I''m a newer to xen. But now I need to do research about
live
>> migration in xen. And now I''m confused with some
questions:
>> 1. Is shadowing page used in both paravirtualization and hvm
>> mode? Since from source code xc_domain_save.c, I see the
>> following code to get dirty memory bitmap,
>>
>> frc = xc_shadow_control(
>> xch, dom, XEN_DOMCTL_SHADOW_OP_PEEK,
>> HYPERCALL_BUFFER(to_skip),
>> dinfo->p2m_size, NULL, 0, NULL);
>
> From domctl.h
>
> /* Log-dirty bitmap operations. */
> /* Return the bitmap and clean internal copy for next round. */
> #define XEN_DOMCTL_SHADOW_OP_CLEAN 11
> /* Return the bitmap but do not modify internal copy. */
> #define XEN_DOMCTL_SHADOW_OP_PEEK 12
>
> Shadow and logdirty are related, but not the same. Shadow is
> certainly not expected to be used with PV guests (although a PV
> guest specifying autotranslate will be run with shadowing enabled).
>
> ~Andrew
>
>>
>>
>> 2. The strategy about memory allocation in xen, I know that dom0
>> will get all available memory at first, and xen will allocate
>> memory via balloon strategy to domU.
>>
>> And now I need to know how balloon works?
>>
>> Can anyone give me some ideas about questions above.
>>
>> Thanks,
>> Yunbin Wang
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org <mailto:Xen-devel@lists.xen.org>
>> http://lists.xen.org/xen-devel
>
>
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