On 24.07.21 00:10, Peter Xu wrote:
On Fri, Jul 23, 2021 at 09:01:42PM +0200, David Hildenbrand wrote:
It can happen in corner cases and is valid: with the current virtio-mem
spec, guests are allowed to read unplugged memory. This will, for example,
happen on older Linux guests when reading /proc/kcore or (with even older
guests) when dumping guest memory via kdump. These corner cases were the
main reason why the spec allows for it -- until we have guests properly
adjusted such that it won't happen even in corner cases.
A future feature bit will disallow it for the guest: required for supporting
shmem/hugetlb cleanly. With that in place, I agree that we would want to
warn in this case!
OK that makes sense; with the page_size change, feel free to add:
I just realized that relying on the page_size would be wrong.
We migrate TARGET_PAGE_SIZE chunks and the offset might not be page_size
aligned. So if we were to replace TARGET_PAGE_SIZE by rb->page_size, we
might accidentally cover a "too big" range.
Makes sense?
Reviewed-by: Peter Xu <pet...@redhat.com>
--
Thanks,
David / dhildenb
