Re: [Xen-devel] [RFC PATCH 71/84] x86/setup: start tearing down the direct map.

[<hongyax@xxxxxxxxxx>]

On 27/09/2019 15:14, Jan Beulich wrote:
> On 27.09.2019 16:02, hongyax@xxxxxxxxxx wrote:
>
> But then why do the initial so many patches (inherited from Wei)
> convert from domheap to xenheap allocations at all? If your
> approach is to be at least an intermediate goal, then I think the
> order of changes should be such that on-demand mapping of xenheap
> pages occurs first, and then the xenheap -> domheap conversion
> can happen in basically arbitrarily small steps.
There is this problem that anything that maps/unmaps memory in the direct map 
region cannot itself rely on an always-mapped direct map. Unfortunately, if I 
map/unmap xenheap allocations, page table manipulation functions (like 
map_pages_to_xen, alloc_xen_pagetable) themselves rely on an always-mapped 
direct map, which often break if you leave holes in the direct map region. 
Wei's patches with some of my later patches break exactly this dependency, so 
page table manipulations themselves no longer rely on the direct map. Now we 
can actually start tearing down the direct map, including on-demand mapping of 
xenheap in the direct map region.
Hongyan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel