Re: [PATCH v4 2/2] selftests: kvm: Add mem_slot_test test

[Wainer dos Santos Moschetta <wainersm@redhat.com>]

On 4/8/20 10:31 PM, Krish Sadhukhan wrote:
>
> On 4/8/20 3:08 PM, Wainer dos Santos Moschetta wrote:
>> This patch introduces the mem_slot_test test which checks
>> an VM can have added memory slots up to the limit defined in
>> KVM_CAP_NR_MEMSLOTS. Then attempt to add one more slot to
>> verify it fails as expected.
>>
>> Signed-off-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
>> ---
>>   tools/testing/selftests/kvm/.gitignore      |  1 +
>>   tools/testing/selftests/kvm/Makefile        |  3 +
>>   tools/testing/selftests/kvm/mem_slot_test.c | 76 +++++++++++++++++++++
>>   3 files changed, 80 insertions(+)
>>   create mode 100644 tools/testing/selftests/kvm/mem_slot_test.c
>>
>> diff --git a/tools/testing/selftests/kvm/.gitignore 
>> b/tools/testing/selftests/kvm/.gitignore
>> index 16877c3daabf..127d27188427 100644
>> --- a/tools/testing/selftests/kvm/.gitignore
>> +++ b/tools/testing/selftests/kvm/.gitignore
>> @@ -21,4 +21,5 @@
>>   /demand_paging_test
>>   /dirty_log_test
>>   /kvm_create_max_vcpus
>> +/mem_slot_test
>>   /steal_time
>> diff --git a/tools/testing/selftests/kvm/Makefile 
>> b/tools/testing/selftests/kvm/Makefile
>> index 712a2ddd2a27..338b6cdce1a0 100644
>> --- a/tools/testing/selftests/kvm/Makefile
>> +++ b/tools/testing/selftests/kvm/Makefile
>> @@ -32,12 +32,14 @@ TEST_GEN_PROGS_x86_64 += clear_dirty_log_test
>>   TEST_GEN_PROGS_x86_64 += demand_paging_test
>>   TEST_GEN_PROGS_x86_64 += dirty_log_test
>>   TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
>> +TEST_GEN_PROGS_x86_64 += mem_slot_test
>>   TEST_GEN_PROGS_x86_64 += steal_time
>>     TEST_GEN_PROGS_aarch64 += clear_dirty_log_test
>>   TEST_GEN_PROGS_aarch64 += demand_paging_test
>>   TEST_GEN_PROGS_aarch64 += dirty_log_test
>>   TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus
>> +TEST_GEN_PROGS_aarch64 += mem_slot_test
>>   TEST_GEN_PROGS_aarch64 += steal_time
>>     TEST_GEN_PROGS_s390x = s390x/memop
>> @@ -46,6 +48,7 @@ TEST_GEN_PROGS_s390x += s390x/sync_regs_test
>>   TEST_GEN_PROGS_s390x += demand_paging_test
>>   TEST_GEN_PROGS_s390x += dirty_log_test
>>   TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
>> +TEST_GEN_PROGS_s390x += mem_slot_test
>>     TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))
>>   LIBKVM += $(LIBKVM_$(UNAME_M))
>> diff --git a/tools/testing/selftests/kvm/mem_slot_test.c 
>> b/tools/testing/selftests/kvm/mem_slot_test.c
>> new file mode 100644
>> index 000000000000..7c1009f0bc07
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/mem_slot_test.c
>> @@ -0,0 +1,76 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * mem_slot_test
>> + *
>> + * Copyright (C) 2020, Red Hat, Inc.
>> + *
>> + * Test suite for memory region operations.
>> + */
>> +#define _GNU_SOURCE /* for program_invocation_short_name */
>> +#include <linux/kvm.h>
>> +#include <sys/mman.h>
>> +
>> +#include "test_util.h"
>> +#include "kvm_util.h"
>> +
>> +/*
>> + * Test it can be added memory slots up to KVM_CAP_NR_MEMSLOTS, then 
>> any
>> + * tentative to add further slots should fail.
>> + */
>> +static void test_add_max_slots(void)
>> +{
>> +    int ret;
>> +    struct kvm_vm *vm;
>> +    uint32_t max_mem_slots;
>> +    uint32_t slot;
>> +    uint64_t guest_addr;
>> +    uint64_t mem_reg_npages;
>> +    uint64_t mem_reg_size;
>> +    void *mem;
>> +
>> +    max_mem_slots = kvm_check_cap(KVM_CAP_NR_MEMSLOTS);
>> +    TEST_ASSERT(max_mem_slots > 0,
>> +            "KVM_CAP_NR_MEMSLOTS should be greater than 0");
>> +    pr_info("Allowed number of memory slots: %i\n", max_mem_slots);
>> +
>> +    vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
>> +
>> +    /*
>> +     * Uses 1MB sized/aligned memory region since this is the minimal
>> +     * required on s390x.
>> +     */
>> +    mem_reg_size = 0x100000;
>> +    mem_reg_npages = vm_calc_num_guest_pages(VM_MODE_DEFAULT, 
>> mem_reg_size);
>> +
>> +    guest_addr = 0x0;
>
>
> Nit: Can't this be initialized where it's defined above ?


I don't have a strong preference. Is it generally initialized on 
definition on kvm (selftests or not) code?


>
>
>> +
>> +    /* Check it can be added memory slots up to the maximum allowed */
>> +    pr_info("Adding slots 0..%i, each memory region with %ldK size\n",
>> +        (max_mem_slots - 1), mem_reg_size >> 10);
>> +    for (slot = 0; slot < max_mem_slots; slot++) {
>> +        vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
>> +                        guest_addr, slot, mem_reg_npages,
>> +                        0);
>> +        guest_addr += mem_reg_size;
>> +    }
>> +
>> +    /* Check it cannot be added memory slots beyond the limit */
>> +    mem = mmap(NULL, mem_reg_size, PROT_READ | PROT_WRITE,
>> +           MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>> +    TEST_ASSERT(mem != MAP_FAILED, "Failed to mmap() host");
>> +
>> +    ret = ioctl(vm_get_fd(vm), KVM_SET_USER_MEMORY_REGION,
>> +            &(struct kvm_userspace_memory_region) {slot, 0, guest_addr,
>> +            mem_reg_size, (uint64_t) mem});
>> +    TEST_ASSERT(ret == -1 && errno == EINVAL,
>> +            "Adding one more memory slot should fail with EINVAL");
>
>
> Why not add a test here for adding memory at an existing slot ?

Good question.

I'm working on another test which should check it cannot be added 
overlapping slots. I will send it in a separate patch series, depending 
on the fate of this one. :)

More precisely, those are the cases I will cover on this new test:


                 0x100000  0x300000
           0x0         0x200000 0x400000
  slot0 |              |---2MB--|                         (SUCCESS)
  slot1       |---2MB--|                                  (FAIL)
  slot2 |---2MB--|                                        (SUCCESS)
  slot3                |---2MB--|                         (FAIL)
  slot4                         |---2MB--|                (FAIL)
  slot5                               |---2MB--|          (SUCCESS)

Thanks!

Wainer

>
>
>> +
>> +    munmap(mem, mem_reg_size);
>> +    kvm_vm_free(vm);
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> +    test_add_max_slots();
>> +    return 0;
>> +}
>