Re: [PATCH V2] SelfTest: KVM: Drop Asserts for madvise MADV_NOHUGEPAGE failure

Andrew Jones
2018-11-16T12:59:07Z

On Fri, Nov 16, 2018 at 01:50:55PM +0200, Ahmed Abd El Mawgood wrote:
> From: Ahmed Abd El Mawgood <ahmedsoliman@mena.vt.edu>
>
> madvise() returns -1 without CONFIG_TRANSPARENT_HUGEPAGE=y. That would
> trigger asserts when checking for return value of madvice. Following
> similar decision to [1]. I thought it is ok to assume that madvise()
> MADV_NOHUGEPAGE failures implies that THP is not supported by host kernel.
>
> Other options was to check for Transparent Huge Page support in
> /sys/kernel/mm/transparent_hugepage/enabled.
>
> -- links --
> [1] https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg04514.html
>
> Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman@mena.vt.edu>
> ---
> tools/testing/selftests/kvm/lib/kvm_util.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 1b41e71283d5..437c5bb48061 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -586,14 +586,23 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> src_type == VM_MEM_SRC_ANONYMOUS_THP ? huge_page_size : 1);
>
> /* As needed perform madvise */
> - if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
> + if (src_type == VM_MEM_SRC_ANONYMOUS) {
> + /*
> + * Neglect madvise error because it is ok to not have THP
> + * support in this case.
> + */
> + madvise(region->host_mem, npages * vm->page_size,
> + MADV_NOHUGEPAGE);
> + } else if (src_type == VM_MEM_SRC_ANONYMOUS_THP) {
> ret = madvise(region->host_mem, npages * vm->page_size,
> - src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
> + MADV_HUGEPAGE);
> TEST_ASSERT(ret == 0, "madvise failed,\n"
> - " addr: %p\n"
> - " length: 0x%lx\n"
> - " src_type: %x",
> - region->host_mem, npages * vm->page_size, src_type);
> + "Does the kernel have CONFIG_TRANSPARENT_HUGEPAGE=y\n"
> + " addr: %p\n"
> + " length: 0x%lx\n"
> + " src_type: %x\n",
> + region->host_mem, npages * vm->page_size,
> + src_type);
> }
>
> region->unused_phy_pages = sparsebit_alloc();
> --
> 2.18.1
>

Reviewed-by: Andrew Jones <drjones@redhat.com>