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    SubjectRe: [RFC PATCH v2 6/7] KVM: selftests: Adapt vm_userspace_mem_region_add to new helpers
    On Wed, Feb 24, 2021 at 10:03 PM Yanan Wang <wangyanan55@huawei.com> wrote:
    >
    > With VM_MEM_SRC_ANONYMOUS_THP specified in vm_userspace_mem_region_add(),
    > we have to get the transparent hugepage size for HVA alignment. With the
    > new helpers, we can use get_backing_src_pagesz() to check whether THP is
    > configured and then get the exact configured hugepage size.
    >
    > As different architectures may have different THP page sizes configured,
    > this can get the accurate THP page sizes on any platform.
    >
    > Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
    > ---
    > tools/testing/selftests/kvm/lib/kvm_util.c | 27 +++++++---------------
    > 1 file changed, 8 insertions(+), 19 deletions(-)
    >
    > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
    > index b91c8e3a7ee1..0105fbfed036 100644
    > --- a/tools/testing/selftests/kvm/lib/kvm_util.c
    > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
    > @@ -18,7 +18,6 @@
    > #include <unistd.h>
    > #include <linux/kernel.h>
    >
    > -#define KVM_UTIL_PGS_PER_HUGEPG 512
    > #define KVM_UTIL_MIN_PFN 2
    >
    > /* Aligns x up to the next multiple of size. Size must be a power of 2. */
    > @@ -686,7 +685,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
    > {
    > int ret;
    > struct userspace_mem_region *region;
    > - size_t huge_page_size = KVM_UTIL_PGS_PER_HUGEPG * vm->page_size;
    > + size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
    > size_t alignment;
    >
    > TEST_ASSERT(vm_adjust_num_guest_pages(vm->mode, npages) == npages,
    > @@ -748,7 +747,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
    > #endif
    >
    > if (src_type == VM_MEM_SRC_ANONYMOUS_THP)
    > - alignment = max(huge_page_size, alignment);
    > + alignment = max(backing_src_pagesz, alignment);
    >
    > /* Add enough memory to align up if necessary */
    > if (alignment > 1)
    > @@ -767,22 +766,12 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
    > region->host_mem = align(region->mmap_start, alignment);
    >
    > /* As needed perform madvise */
    > - if (src_type == VM_MEM_SRC_ANONYMOUS || src_type == VM_MEM_SRC_ANONYMOUS_THP) {
    > - struct stat statbuf;
    > -
    > - ret = stat("/sys/kernel/mm/transparent_hugepage", &statbuf);
    > - TEST_ASSERT(ret == 0 || (ret == -1 && errno == ENOENT),
    > - "stat /sys/kernel/mm/transparent_hugepage");
    > -
    > - TEST_ASSERT(ret == 0 || src_type != VM_MEM_SRC_ANONYMOUS_THP,
    > - "VM_MEM_SRC_ANONYMOUS_THP requires THP to be configured in the host kernel");
    > -
    > - if (ret == 0) {
    > - ret = madvise(region->host_mem, npages * vm->page_size,
    > - src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
    > - TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %x",
    > - region->host_mem, npages * vm->page_size, src_type);
    > - }
    > + if (src_type <= VM_MEM_SRC_ANONYMOUS_THP && thp_configured()) {

    This check relies on an unstated property of the backing src type
    enums where VM_MEM_SRC_ANONYMOUS and VM_MEM_SRC_ANONYMOUS_THP are
    declared first.
    It would probably be more readable for folks if the check was explicit:
    if ((src_type == VM_MEM_SRC_ANONYMOUS || src_type ==
    VM_MEM_SRC_ANONYMOUS_THP) && thp_configured()) {


    > + ret = madvise(region->host_mem, npages * vm->page_size,
    > + src_type == VM_MEM_SRC_ANONYMOUS ? MADV_NOHUGEPAGE : MADV_HUGEPAGE);
    > + TEST_ASSERT(ret == 0, "madvise failed, addr: %p length: 0x%lx src_type: %s",
    > + region->host_mem, npages * vm->page_size,
    > + vm_mem_backing_src_alias(src_type)->name);
    > }
    >
    > region->unused_phy_pages = sparsebit_alloc();
    > --
    > 2.19.1
    >

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