[Xen-devel] Question on balloon driver & guest memory reservation!

["Jayaraman, Bhaskar" <Bhaskar.Jayaraman@xxxxxxx>]

Hi, from the balloon driver for HVM Linux guests, I can see that only direct map addresses or logical addresses can be used. So if a 32-bit (PAE or otherwise) guest uses the balloon driver it can allocate up to a maximum of where the low memory addresses end (GFP_KERNEL) 896 MB or from the fixed map area of 128 MB which could be from low or high mem. Please let me know if my assumption is correct.

 

2^nd unlike a PV guest, where after alloc_empty_pages_and_pagevec (e.g. blkback) and mapping in memory from another domain, if I alloc empty balloon pages in an HVM and then try to access the page how will it be handled by Xen? I see that a PV guest crashes if I access an empty page without mapping anything into its place.

 

Regards,

Bhaskar.

 

 

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