Alexey Kardashevskiy [off-list ref] writes:

The CMA pages migration code does not support compound pages at
the moment so it performs few tests before proceeding to actual page
migration.

One of the tests - PageTransHuge() - has VM_BUG_ON_PAGE(PageTail()) as
it should be called on head pages. Since we also test for PageCompound(),
and it contains PageTail(), we can simply move PageCompound() in front
of PageTransHuge() and therefore avoid possible VM_BUG_ON_PAGE.

Signed-off-by: Alexey Kardashevskiy <redacted>
---

Some of actual POWER8 systems do crash on that BUG_ON.

So this is:

Fixes: 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate pinned pages out of CMA")

And therefore:

Cc: stable@vger.kernel.org # v4.9+

?

cheers