I've ported selftests from Chao and I [1] while working on hugetlb support
for
guest_mem [2].
In the process, I found some bugs and have some suggestions for guest_mem.
Please see separate commits at [3].
Here are some highlights/questions:
+ "KVM: guest_mem: Explain the use of the uptodate flag for gmem"
+ Generally, uptodate flags means that the contents of this page match
the
backing store. Since gmem is memory-backed, does "uptodate" for gmem
mean
"zeroed"?
+ "KVM: guest_mem: Don't re-mark accessed after getting a folio" and "KVM:
guest_mem: Don't set dirty flag for folio"
+ Do we need to folio_mark_accessed(), when it was created with
FGP_ACCESSED?
+ What is the significance of these LRU flags when gmem doesn't support
swapping/eviction?
+ "KVM: guest_mem: Align so that at least 1 page is allocated"
+ Bug in current implementation: without this alignment, fallocate() of
a
size less than the gmem page size will result in no allocation at all
+ Both shmem and hugetlbfs perform this alignment
+ "KVM: guest_mem: Add alignment checks"
+ Implemented the alignment checks for guest_mem because hugetlb on gmem
would hit a BUG_ON without this check
+ "KVM: guest_mem: Prevent overflows in kvm_gmem_invalidate_begin()"
+ Sean fixed a bug in the offset-to-gfn conversion in
kvm_gmem_invalidate_begin() earlier, adding a WARN_ON_ONCE()
+ Code will always hit WARN_ON_ONCE() when the entire file is closed
and all
offsets are invalidated, so WARN_ON_ONCE() should be removed
+ Vishal noticed that the conversion might result in an overflow, so I
fixed
that
+ And of course, hugetlb support! Please let me know what you think of the
approach proposed at [2].
[1]
https://lore.kernel.org/all/cover.1678926164.git.ackerleytng@xxxxxxxxxx/T/
[2]
https://lore.kernel.org/lkml/cover.1686077275.git.ackerleytng@xxxxxxxxxx/T/
[3] https://github.com/googleprodkernel/linux-cc/tree/gmem-hugetlb-rfc-v1
