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Re: [Xen-devel] [PATCH v3 29/32] libxc/xen: introduce HVM_PARAM_FIRST_FREE_PFN

El 10/07/15 a les 21.05, Konrad Rzeszutek Wilk ha escrit:
> On Fri, Jul 03, 2015 at 01:35:07PM +0200, Roger Pau Monne wrote:
>> This HVM parameter returns the first free pfn after all the special pages.
> Could you describe how the layout of PFNs is now for the HVM guests?
> Is there some document that outlines it? I know that for PV we do 
> have it as part of the start_info structure but not sure about HVM?
>> It can be used by guests to figure out the first free memory address after
>> the kernel, ramdisk and special pages. This is interesting for compatibility
> So you mention it here, perhaps there should be an document
> mentioning this. Or the header for the PFNs?
>> reasons in case more special pages are later added, older guests can still
>> use this parameter to figure out the first free address, ignoring newly
>> added special pages.
> And presumarily figure out the 'special PFN's and mark them
> as reserved? Are those PFNs in the E820 as RESERVED?
> We should also put some restrictions in the code then to make sure
> that there will never be any HVM_PARAM_*PFN _after_ this PFN.

I don't think we need this any longer, with the new approach that I've
described in the previous email (see the reply to "libxc: change the
position of the special pages") there's no need to introduce this new
HVMPARAM, and the special pages will be marked as "reserved" in the
memory map, with the exception of the command line and the module list
special pages, that are appended after the kernel/initramfs.


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