Re: [PATCH] tests: kvm: Check for a kernel warning

[Krish Sadhukhan <krish.sadhukhan@oracle.com>]

On 06/18/2019 07:13 AM, Aaron Lewis wrote:
> On Fri, May 31, 2019 at 7:14 AM Aaron Lewis <aaronlewis@google.com> wrote:
>> When running with /sys/module/kvm_intel/parameters/unrestricted_guest=N,
>> test that a kernel warning does not occur informing us that
>> vcpu->mmio_needed=1.  This can happen when KVM_RUN is called after a
>> triple fault.
>> This test was made to detect a bug that was reported by Syzkaller
>> (https://groups.google.com/forum/#!topic/syzkaller/lHfau8E3SOE) and
>> fixed with commit bbeac2830f4de ("KVM: X86: Fix residual mmio emulation
>> request to userspace").
>>
>> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
>> Reviewed-by: Jim Mattson <jmattson@google.com>
>> Reviewed-by: Peter Shier <pshier@google.com>
>> ---
>>   tools/testing/selftests/kvm/.gitignore        |   1 +
>>   tools/testing/selftests/kvm/Makefile          |   1 +
>>   .../testing/selftests/kvm/include/kvm_util.h  |   2 +
>>   .../selftests/kvm/include/x86_64/processor.h  |   2 +
>>   tools/testing/selftests/kvm/lib/kvm_util.c    |  36 +++++
>>   .../selftests/kvm/lib/x86_64/processor.c      |  16 +++
>>   .../selftests/kvm/x86_64/mmio_warning_test.c  | 126 ++++++++++++++++++
>>   7 files changed, 184 insertions(+)
>>   create mode 100644 tools/testing/selftests/kvm/x86_64/mmio_warning_test.c
>>
>> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
>> index df1bf9230a74..41266af0d3dc 100644
>> --- a/tools/testing/selftests/kvm/.gitignore
>> +++ b/tools/testing/selftests/kvm/.gitignore
>> @@ -2,6 +2,7 @@
>>   /x86_64/evmcs_test
>>   /x86_64/hyperv_cpuid
>>   /x86_64/kvm_create_max_vcpus
>> +/x86_64/mmio_warning_test
>>   /x86_64/platform_info_test
>>   /x86_64/set_sregs_test
>>   /x86_64/smm_test
>> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
>> index 79c524395ebe..670b938f1049 100644
>> --- a/tools/testing/selftests/kvm/Makefile
>> +++ b/tools/testing/selftests/kvm/Makefile
>> @@ -22,6 +22,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_close_while_nested_test
>>   TEST_GEN_PROGS_x86_64 += x86_64/smm_test
>>   TEST_GEN_PROGS_x86_64 += x86_64/kvm_create_max_vcpus
>>   TEST_GEN_PROGS_x86_64 += x86_64/vmx_set_nested_state_test
>> +TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
>>   TEST_GEN_PROGS_x86_64 += dirty_log_test
>>   TEST_GEN_PROGS_x86_64 += clear_dirty_log_test
>>
>> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
>> index 8c6b9619797d..c5c427c86598 100644
>> --- a/tools/testing/selftests/kvm/include/kvm_util.h
>> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
>> @@ -137,6 +137,8 @@ struct kvm_vm *vm_create_default(uint32_t vcpuid, uint64_t extra_mem_size,
>>                                   void *guest_code);
>>   void vm_vcpu_add_default(struct kvm_vm *vm, uint32_t vcpuid, void *guest_code);
>>
>> +bool vm_is_unrestricted_guest(struct kvm_vm *vm);
>> +
>>   struct kvm_userspace_memory_region *
>>   kvm_userspace_memory_region_find(struct kvm_vm *vm, uint64_t start,
>>                                   uint64_t end);
>> diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
>> index 6063d5b2f356..af4d26de32d1 100644
>> --- a/tools/testing/selftests/kvm/include/x86_64/processor.h
>> +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
>> @@ -303,6 +303,8 @@ static inline unsigned long get_xmm(int n)
>>          return 0;
>>   }
>>
>> +bool is_intel_cpu(void);
>> +
>>   struct kvm_x86_state;
>>   struct kvm_x86_state *vcpu_save_state(struct kvm_vm *vm, uint32_t vcpuid);
>>   void vcpu_load_state(struct kvm_vm *vm, uint32_t vcpuid,
>> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
>> index e9113857f44e..b93b09ad9a11 100644
>> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
>> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
>> @@ -1584,3 +1584,39 @@ void *addr_gva2hva(struct kvm_vm *vm, vm_vaddr_t gva)
>>   {
>>          return addr_gpa2hva(vm, addr_gva2gpa(vm, gva));
>>   }
>> +
>> +/*
>> + * Is Unrestricted Guest
>> + *
>> + * Input Args:
>> + *   vm - Virtual Machine
>> + *
>> + * Output Args: None
>> + *
>> + * Return: True if the unrestricted guest is set to 'Y', otherwise return false.
>> + *
>> + * Check if the unrestricted guest flag is enabled.
>> + */
>> +bool vm_is_unrestricted_guest(struct kvm_vm *vm)
>> +{
>> +       char val = 'N';
>> +       size_t count;
>> +       FILE *f;
>> +
>> +       if (vm == NULL) {
>> +               /* Ensure that the KVM vendor-specific module is loaded. */
>> +               f = fopen(KVM_DEV_PATH, "r");
>> +               TEST_ASSERT(f != NULL, "Error in opening KVM dev file: %d",
>> +                           errno);
>> +               fclose(f);
>> +       }
>> +
>> +       f = fopen("/sys/module/kvm_intel/parameters/unrestricted_guest", "r");
>> +       if (f) {
>> +               count = fread(&val, sizeof(char), 1, f);
>> +               TEST_ASSERT(count == 1, "Unable to read from param file.");
>> +               fclose(f);
>> +       }
>> +
>> +       return val == 'Y';
>> +}
>> diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
>> index dc7fae9fa424..bcc0e70e1856 100644
>> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
>> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
>> @@ -1139,3 +1139,19 @@ void vcpu_load_state(struct kvm_vm *vm, uint32_t vcpuid, struct kvm_x86_state *s
>>                          r);
>>          }
>>   }
>> +
>> +bool is_intel_cpu(void)
>> +{
>> +       int eax, ebx, ecx, edx;
>> +       const uint32_t *chunk;
>> +       const int leaf = 0;
>> +
>> +       __asm__ __volatile__(
>> +               "cpuid"
>> +               : /* output */ "=a"(eax), "=b"(ebx),
>> +                 "=c"(ecx), "=d"(edx)
>> +               : /* input */ "0"(leaf), "2"(0));
>> +
>> +       chunk = (const uint32_t *)("GenuineIntel");
>> +       return (ebx == chunk[0] && edx == chunk[1] && ecx == chunk[2]);
>> +}
>> diff --git a/tools/testing/selftests/kvm/x86_64/mmio_warning_test.c b/tools/testing/selftests/kvm/x86_64/mmio_warning_test.c
>> new file mode 100644
>> index 000000000000..00bb97d76000
>> --- /dev/null
>> +++ b/tools/testing/selftests/kvm/x86_64/mmio_warning_test.c
>> @@ -0,0 +1,126 @@
>> +/*
>> + * mmio_warning_test
>> + *
>> + * Copyright (C) 2019, Google LLC.
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2.
>> + *
>> + * Test that we don't get a kernel warning when we call KVM_RUN after a
>> + * triple fault occurs.  To get the triple fault to occur we call KVM_RUN
>> + * on a VCPU that hasn't been properly setup.
>> + *
>> + */
>> +
>> +#define _GNU_SOURCE
>> +#include <fcntl.h>
>> +#include <kvm_util.h>
>> +#include <linux/kvm.h>
>> +#include <processor.h>
>> +#include <pthread.h>
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <sys/ioctl.h>
>> +#include <sys/mman.h>
>> +#include <sys/stat.h>
>> +#include <sys/types.h>
>> +#include <sys/wait.h>
>> +#include <test_util.h>
>> +#include <unistd.h>
>> +
>> +#define NTHREAD 4
>> +#define NPROCESS 5
>> +
>> +struct thread_context {
>> +       int kvmcpu;
>> +       struct kvm_run *run;
>> +};
>> +
>> +void *thr(void *arg)
>> +{
>> +       struct thread_context *tc = (struct thread_context *)arg;
>> +       int res;
>> +       int kvmcpu = tc->kvmcpu;
>> +       struct kvm_run *run = tc->run;
>> +
>> +       res = ioctl(kvmcpu, KVM_RUN, 0);
>> +       printf("ret1=%d exit_reason=%d suberror=%d\n",
>> +               res, run->exit_reason, run->internal.suberror);
>> +
>> +       return 0;
>> +}
>> +
>> +void test(void)
>> +{
>> +       int i, kvm, kvmvm, kvmcpu;
>> +       pthread_t th[NTHREAD];
>> +       struct kvm_run *run;
>> +       struct thread_context tc;
>> +
>> +       kvm = open("/dev/kvm", O_RDWR);
>> +       TEST_ASSERT(kvm != -1, "failed to open /dev/kvm");
>> +       kvmvm = ioctl(kvm, KVM_CREATE_VM, 0);
>> +       TEST_ASSERT(kvmvm != -1, "KVM_CREATE_VM failed");
>> +       kvmcpu = ioctl(kvmvm, KVM_CREATE_VCPU, 0);
>> +       TEST_ASSERT(kvmcpu != -1, "KVM_CREATE_VCPU failed");
>> +       run = (struct kvm_run *)mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_SHARED,
>> +                                   kvmcpu, 0);
>> +       tc.kvmcpu = kvmcpu;
>> +       tc.run = run;
>> +       srand(getpid());
>> +       for (i = 0; i < NTHREAD; i++) {
>> +               pthread_create(&th[i], NULL, thr, (void *)(uintptr_t)&tc);
>> +               usleep(rand() % 10000);
>> +       }
>> +       for (i = 0; i < NTHREAD; i++)
>> +               pthread_join(th[i], NULL);
>> +}
>> +
>> +int get_warnings_count(void)
>> +{
>> +       int warnings;
>> +       FILE *f;
>> +
>> +       f = popen("dmesg | grep \"WARNING:\" | wc -l", "r");
>> +       fscanf(f, "%d", &warnings);
>> +       fclose(f);
>> +
>> +       return warnings;
>> +}
>> +
>> +int main(void)
>> +{
>> +       int warnings_before, warnings_after;
>> +
>> +       if (!is_intel_cpu()) {
>> +               printf("Must be run on an Intel CPU, skipping test\n");
>> +               exit(KSFT_SKIP);
>> +       }
>> +
>> +       if (vm_is_unrestricted_guest(NULL)) {
>> +               printf("Unrestricted guest must be disabled, skipping test\n");
>> +               exit(KSFT_SKIP);
>> +       }
>> +
>> +       warnings_before = get_warnings_count();
>> +
>> +       for (int i = 0; i < NPROCESS; ++i) {
>> +               int status;
>> +               int pid = fork();
>> +
>> +               if (pid < 0)
>> +                       exit(1);
>> +               if (pid == 0) {
>> +                       test();
>> +                       exit(0);
>> +               }
>> +               while (waitpid(pid, &status, __WALL) != pid)
>> +                       ;
>> +       }
>> +
>> +       warnings_after = get_warnings_count();

Since you are grep'ing for the word "WARNING",  is there a possibility 
that the test can detect a false positive based on Warnings generated 
due to some other cause while it ran ?

>> +       TEST_ASSERT(warnings_before == warnings_after,
>> +                  "Warnings found in kernel.  Run 'dmesg' to inspect them.");
>> +
>> +       return 0;
>> +}
>> --
>> 2.22.0.rc1.311.g5d7573a151-goog
>>
> ping