KVM: selftests: Add wrfract to common guest code

Wrfract will be used by the dirty logging perf test introduced later in
this series to dirty memory sparsely.

This series was tested by running the following invocations on an Intel
Skylake machine:
dirty_log_perf_test -b 20m -i 100 -v 64
dirty_log_perf_test -b 20g -i 5 -v 4
dirty_log_perf_test -b 4g -i 5 -v 32
demand_paging_test -b 20m -v 64
demand_paging_test -b 20g -v 4
demand_paging_test -b 4g -v 32
All behaved as expected.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20201027233733.1484855-5-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 7de6feb000760659c0706f666bc1db4a292eb028..47defc65aedac39e909af22ef17ddc45c0de81c2 100644 (file)
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -266,6 +266,8 @@ static void run_test(enum vm_guest_mode mode, bool use_uffd,
 
        vm = create_vm(mode, vcpus, vcpu_memory_bytes);
 
+       perf_test_args.wr_fract = 1;
+
        guest_data_prototype = malloc(perf_test_args.host_page_size);
        TEST_ASSERT(guest_data_prototype,
                    "Failed to allocate buffer for guest data pattern");

diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
index 838f946700f0c0f4d8df93fdead38a9c79338f00..1716300469c04a2e4aaf8f78e1026d33ceb2cca4 100644 (file)
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -46,6 +46,7 @@ struct perf_test_args {
        struct kvm_vm *vm;
        uint64_t host_page_size;
        uint64_t guest_page_size;
+       int wr_fract;
 
        struct vcpu_args vcpu_args[MAX_VCPUS];
 };
@@ -72,7 +73,10 @@ static void guest_code(uint32_t vcpu_id)
        for (i = 0; i < pages; i++) {
                uint64_t addr = gva + (i * perf_test_args.guest_page_size);
 
-               *(uint64_t *)addr = 0x0123456789ABCDEF;
+               if (i % perf_test_args.wr_fract == 0)
+                       *(uint64_t *)addr = 0x0123456789ABCDEF;
+               else
+                       READ_ONCE(*(uint64_t *)addr);
        }
 
        GUEST_SYNC(1);