Re: [PATCH v3 4/8] KVM: selftests: Add memory size parameter to the demand paging test

On Tue, Jan 7, 2020 at 7:02 AM Andrew Jones drjones@redhat.com wrote:

On Mon, Dec 16, 2019 at 01:38:57PM -0800, Ben Gardon wrote:

...

Add an argument to allow the demand paging test to work on larger and smaller guest sizes.

Signed-off-by: Ben Gardon bgardon@google.com

.../selftests/kvm/demand_paging_test.c | 56 ++++++++++++------- 1 file changed, 35 insertions(+), 21 deletions(-)

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c index 11de5b58995fb..4aa90a3fce99c 100644 --- a/tools/testing/selftests/kvm/demand_paging_test.c +++ b/tools/testing/selftests/kvm/demand_paging_test.c @@ -32,6 +32,8 @@ /* Default guest test virtual memory offset */ #define DEFAULT_GUEST_TEST_MEM 0xc0000000

+#define DEFAULT_GUEST_TEST_MEM_SIZE (1 << 30) /* 1G */

/*

• Guest/Host shared variables. Ensure addr_gva2hva() and/or
• sync_global_to/from_guest() are used when accessing from

@@ -264,11 +266,10 @@ static int setup_demand_paging(struct kvm_vm *vm, return 0; }

-#define GUEST_MEM_SHIFT 30 /* 1G */ #define PAGE_SHIFT_4K 12

static void run_test(enum vm_guest_mode mode, bool use_uffd,

•              useconds_t uffd_delay)
  

•              useconds_t uffd_delay, uint64_t guest_memory_bytes)
  

{ pthread_t vcpu_thread; pthread_t uffd_handler_thread; @@ -276,33 +277,40 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd, int r;

  /*

•  * We reserve page table for 2 times of extra dirty mem which
  

•  * will definitely cover the original (1G+) test range.  Here
  

•  * we do the calculation with 4K page size which is the
  

•  * smallest so the page number will be enough for all archs
  

•  * (e.g., 64K page size guest will need even less memory for
  

•  * page tables).
  

•  * We reserve page table for twice the ammount of memory we intend
  

•  * to use in the test region for demand paging. Here we do the
  

•  * calculation with 4K page size which is the smallest so the page
  

•  * number will be enough for all archs. (e.g., 64K page size guest
  

•  * will need even less memory for page tables).
   */
  vm = create_vm(mode, VCPU_ID,
  

•                2ul << (GUEST_MEM_SHIFT - PAGE_SHIFT_4K),
  

•                (2 * guest_memory_bytes) >> PAGE_SHIFT_4K,
                 guest_code);
  
  guest_page_size = vm_get_page_size(vm);
  

• /*
  

•  * A little more than 1G of guest page sized pages.  Cover the
  

•  * case where the size is not aligned to 64 pages.
  

•  */
  

• guest_num_pages = (1ul << (GUEST_MEM_SHIFT -
  

•                            vm_get_page_shift(vm))) + 16;
  

• TEST_ASSERT(guest_memory_bytes % guest_page_size == 0,
  

•             "Guest memory size is not guest page size aligned.");
  

• guest_num_pages = guest_memory_bytes / guest_page_size;
  

#ifdef __s390x__ /* Round up to multiple of 1M (segment size) */ guest_num_pages = (guest_num_pages + 0xff) & ~0xffUL; #endif

• /*
  

•  * If there should be more memory in the guest test region than there
  

•  * can be pages in the guest, it will definitely cause problems.
  

•  */
  

• TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
  

•             "Requested more guest memory than address space allows.\n"
  

•             "    guest pages: %lx max gfn: %lx\n",
  

•             guest_num_pages, vm_get_max_gfn(vm));
  
  host_page_size = getpagesize();
  

• host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
  

•                  !!((guest_num_pages * guest_page_size) %
  

•                     host_page_size);
  

• TEST_ASSERT(guest_memory_bytes % host_page_size == 0,
  

•             "Guest memory size is not host page size aligned.");
  

• host_num_pages = guest_memory_bytes / host_page_size;
  
  guest_test_phys_mem = (vm_get_max_gfn(vm) - guest_num_pages) *
                        guest_page_size;
  

@@ -381,7 +389,8 @@ static void help(char *name) int i;

  puts("");

• printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n", name);
  

• printf("usage: %s [-h] [-m mode] [-u] [-d uffd_delay_usec]\n"
  

•        "          [-b bytes test memory]\n", name);
  printf(" -m: specify the guest mode ID to test\n"
         "     (default: test all supported modes)\n"
         "     This option may be used multiple times.\n"
  

@@ -395,6 +404,8 @@ static void help(char *name) printf(" -d: add a delay in usec to the User Fault\n" " FD handler to simulate demand paging\n" " overheads. Ignored without -u.\n");

• printf(" -b: specify the number of bytes of memory which should be\n"
  

•        "     allocated to the guest.\n");
  

Can we input in megabytes instead? And also it might be nice to output the default size here.

I added a little function to parse size arguments so users can specify 2M or 7G. I also changed this to print the default value.

...

  puts("");
  exit(0);

} @@ -402,6 +413,7 @@ static void help(char *name) int main(int argc, char *argv[]) { bool mode_selected = false;

• uint64_t guest_memory_bytes = DEFAULT_GUEST_TEST_MEM_SIZE;
  unsigned int mode;
  int opt, i;
  bool use_uffd = false;
  

@@ -414,7 +426,7 @@ int main(int argc, char *argv[]) vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true); #endif

• while ((opt = getopt(argc, argv, "hm:ud:")) != -1) {
  

• while ((opt = getopt(argc, argv, "hm:ud:b:")) != -1) {
          switch (opt) {
          case 'm':
                  if (!mode_selected) {
  

@@ -435,6 +447,8 @@ int main(int argc, char *argv[]) TEST_ASSERT(uffd_delay >= 0, "A negative UFFD delay is not supported."); break;

•         case 'b':
  

•                 guest_memory_bytes = strtoull(optarg, NULL, 0);
  

Missing break. So it doesn't look like this was tested.

Woops, you're right, I must not have tested this commit. The break is added in commit 6/8 and I only tested at the end of the series. I'll have the break in this commit in the next version of this series.

...

          case 'h':
          default:
                  help(argv[0]);

@@ -448,7 +462,7 @@ int main(int argc, char *argv[]) TEST_ASSERT(vm_guest_mode_params[i].supported, "Guest mode ID %d (%s) not supported.", i, vm_guest_mode_string(i));

•         run_test(i, use_uffd, uffd_delay);
  

•         run_test(i, use_uffd, uffd_delay, guest_memory_bytes);
  }
  
  return 0;
  

-- 2.24.1.735.g03f4e72817-goog

Thanks, drew