| Date | Tue, 19 May 2015 16:23:03 +0100 | From | David Vrabel <> | Subject | Re: [Xen-devel] [RFC 15/23] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux |
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On 14/05/15 18:00, Julien Grall wrote: > For ARM64 guests, Linux is able to support either 64K or 4K page > granularity. Although, the hypercall interface is always based on 4K > page granularity. > > With 64K page granuliarty, a single page will be spread over multiple > Xen frame. > > When a driver request/free a balloon page, the balloon driver will have > to split the Linux page in 4K chunk before asking Xen to add/remove the > frame from the guest. > > Note that this can work on any page granularity assuming it's a multiple > of 4K. [...] > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -91,7 +91,7 @@ struct balloon_stats balloon_stats; > EXPORT_SYMBOL_GPL(balloon_stats); > > /* We increase/decrease in batches which fit in a page */ > -static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)]; > +static xen_pfn_t frame_list[XEN_PAGE_SIZE / sizeof(unsigned long)];
PAGE_SIZE is appropriate here, since this is a guest-side array.
> + if (!(i % XEN_PFN_PER_PAGE)) {
Ick. Can you refactor this into a loop per page calling a function that loops per MFN.
Also similar tests elsewhere.
David
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