On Fri, Jan 26, 2024 at 12:39:49PM -0800, Sean Christopherson wrote:
> +David
>
[ ... ]
> >
> > /*
> > @@ -192,7 +193,6 @@ static void run_test(enum vm_guest_mode mode, void *unused)
> > * memory again, the page counts should be the same as they were
> > * right after initial population of memory.
> > */
> > - TEST_ASSERT_EQ(stats_populated.pages_4k, stats_repopulated.pages_4k);
> > TEST_ASSERT_EQ(stats_populated.pages_2m, stats_repopulated.pages_2m);
> > TEST_ASSERT_EQ(stats_populated.pages_1g, stats_repopulated.pages_1g);
>
> Isn't it possible that something other than guest data could be mapped by THP
> hugepage, and that that hugepage could get shattered between the initial run and
> the re-population run?
Good catch, I found that if the backing source is specified as THP, all hugepages
can also be migrated.
>
> The test knows (or at least, darn well should know) exactly how much memory is
> being dirty logged. Rather that rely *only* on before/after heuristics, can't
> we assert that the _delta_, i.e. the number of hugepages that are split, and then
> the number of hugepages that are reconstituted, is greater than or equal to the
> size of the memslots being dirty logged?
Due to page migration, the values of get_page_stats() are not available (including
pages_2m and pages_1g), and dirty logging can only count the pages that have been
split. It may be possible to use the existing guest_num_pages to construct the
following assert condition:
guest_num_pages <= the number of dirty pages
Do you think this assert condition is correct and enough?
Thanks,
Tao
>
> > }
> >
> > base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
> > --
> > 2.34.1
> >
