Re: [RFC PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries

From: Juergen Gross
Date: Wed Nov 16 2016 - 01:07:04 EST

On 15/11/16 16:22, Alex Thorlton wrote:
> On Tue, Nov 15, 2016 at 10:55:49AM +0100, Juergen Gross wrote:
>> I'd go with the new error code. What about E2BIG or ENOSPC?
>> I think the hypervisor should fill in the number of entries required
>> in this case.
>> In case nobody objects I can post patches for this purpose (both Xen
>> and Linux).
> This sounds like a good solution to me. I think it's definitely more
> appropriate than simply bumping up the size of xen_e820_map, especially
> considering the fact that it's theoretically possible for the e820 map
> generated by the hypercall to grow too large, even on a non-EFI machine,
> where my change would have no effect.

Well, it won't help with the current hypervisor, so bumping up the size
of xen_e820_map will still be a good idea. I think using E820_X_MAX is
okay since in the end xen_e820_map will be transferred into a struct
e820map which can't hold more than E820_X_MAX entries (additional
entries are ignored here, so this won't let the boot fail).