Re: [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