On Tue, 28 Jun 2022 18:02:28 +1000, Alexey Kardashevskiy wrote:

KVM manages emulated TCE tables for guest LIOBNs by a two level table
which maps up to 128TiB with 16MB IOMMU pages (enabled in QEMU by default)
and MAX_ORDER=11 (the kernel's default). Note that the last level of
the table is allocated when actual TCE is updated.

However these tables are created via ioctl() on kvmfd and the userspace
can trigger WARN_ON_ONCE_GFP(order >= MAX_ORDER, gfp) in mm/page_alloc.c
and flood dmesg.

[...]

Applied to powerpc/topic/ppc-kvm.

[1/1] KVM: PPC: Do not warn when userspace asked for too big TCE table
      https://git.kernel.org/powerpc/c/4dee21e0f2520f5032b0abce0ecae593a71bd19d

cheers