Re: [PATCH 33/34] KVM: selftests: Test KVM exit behavior for private memory/access

[Fuad Tabba]

On Sun, Nov 5, 2023 at 4:35 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> From: Ackerley Tng <ackerleytng@xxxxxxxxxx>
>
> "Testing private access when memslot gets deleted" tests the behavior
> of KVM when a private memslot gets deleted while the VM is using the
> private memslot. When KVM looks up the deleted (slot = NULL) memslot,
> KVM should exit to userspace with KVM_EXIT_MEMORY_FAULT.
>
> In the second test, upon a private access to non-private memslot, KVM
> should also exit to userspace with KVM_EXIT_MEMORY_FAULT.

nit: The commit message is referring to private memslots, which might
need rewording with the latest changes in v14.

> Intentionally don't take a requirement on KVM_CAP_GUEST_MEMFD,
> KVM_CAP_MEMORY_FAULT_INFO, KVM_MEMORY_ATTRIBUTE_PRIVATE, etc., as it's a
> KVM bug to advertise KVM_X86_SW_PROTECTED_VM without its prerequisites.
>
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> [sean: call out the similarities with set_memory_region_test]
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Message-Id: <20231027182217.3615211-36-seanjc@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../kvm/x86_64/private_mem_kvm_exits_test.c   | 120 ++++++++++++++++++
>  2 files changed, 121 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index fd3b30a4ca7b..69ce8e06b3a3 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -92,6 +92,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/nested_exceptions_test
>  TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
>  TEST_GEN_PROGS_x86_64 += x86_64/pmu_event_filter_test
>  TEST_GEN_PROGS_x86_64 += x86_64/private_mem_conversions_test
> +TEST_GEN_PROGS_x86_64 += x86_64/private_mem_kvm_exits_test
>  TEST_GEN_PROGS_x86_64 += x86_64/set_boot_cpu_id
>  TEST_GEN_PROGS_x86_64 += x86_64/set_sregs_test
>  TEST_GEN_PROGS_x86_64 += x86_64/smaller_maxphyaddr_emulation_test
> diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
> new file mode 100644
> index 000000000000..2f02f6128482
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/private_mem_kvm_exits_test.c
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022, Google LLC.

nit: 2023

Nits aside:
Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>
Tested-by: Fuad Tabba <tabba@xxxxxxxxxx>

Cheers,
/fuad




> + */
> +#include <linux/kvm.h>
> +#include <pthread.h>
> +#include <stdint.h>
> +
> +#include "kvm_util.h"
> +#include "processor.h"
> +#include "test_util.h"
> +
> +/* Arbitrarily selected to avoid overlaps with anything else */
> +#define EXITS_TEST_GVA 0xc0000000
> +#define EXITS_TEST_GPA EXITS_TEST_GVA
> +#define EXITS_TEST_NPAGES 1
> +#define EXITS_TEST_SIZE (EXITS_TEST_NPAGES * PAGE_SIZE)
> +#define EXITS_TEST_SLOT 10
> +
> +static uint64_t guest_repeatedly_read(void)
> +{
> +       volatile uint64_t value;
> +
> +       while (true)
> +               value = *((uint64_t *) EXITS_TEST_GVA);
> +
> +       return value;
> +}
> +
> +static uint32_t run_vcpu_get_exit_reason(struct kvm_vcpu *vcpu)
> +{
> +       int r;
> +
> +       r = _vcpu_run(vcpu);
> +       if (r) {
> +               TEST_ASSERT(errno == EFAULT, KVM_IOCTL_ERROR(KVM_RUN, r));
> +               TEST_ASSERT_EQ(vcpu->run->exit_reason, KVM_EXIT_MEMORY_FAULT);
> +       }
> +       return vcpu->run->exit_reason;
> +}
> +
> +const struct vm_shape protected_vm_shape = {
> +       .mode = VM_MODE_DEFAULT,
> +       .type = KVM_X86_SW_PROTECTED_VM,
> +};
> +
> +static void test_private_access_memslot_deleted(void)
> +{
> +       struct kvm_vm *vm;
> +       struct kvm_vcpu *vcpu;
> +       pthread_t vm_thread;
> +       void *thread_return;
> +       uint32_t exit_reason;
> +
> +       vm = vm_create_shape_with_one_vcpu(protected_vm_shape, &vcpu,
> +                                          guest_repeatedly_read);
> +
> +       vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
> +                                   EXITS_TEST_GPA, EXITS_TEST_SLOT,
> +                                   EXITS_TEST_NPAGES,
> +                                   KVM_MEM_GUEST_MEMFD);
> +
> +       virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);
> +
> +       /* Request to access page privately */
> +       vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
> +
> +       pthread_create(&vm_thread, NULL,
> +                      (void *(*)(void *))run_vcpu_get_exit_reason,
> +                      (void *)vcpu);
> +
> +       vm_mem_region_delete(vm, EXITS_TEST_SLOT);
> +
> +       pthread_join(vm_thread, &thread_return);
> +       exit_reason = (uint32_t)(uint64_t)thread_return;
> +
> +       TEST_ASSERT_EQ(exit_reason, KVM_EXIT_MEMORY_FAULT);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.flags, KVM_MEMORY_EXIT_FLAG_PRIVATE);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.gpa, EXITS_TEST_GPA);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.size, EXITS_TEST_SIZE);
> +
> +       kvm_vm_free(vm);
> +}
> +
> +static void test_private_access_memslot_not_private(void)
> +{
> +       struct kvm_vm *vm;
> +       struct kvm_vcpu *vcpu;
> +       uint32_t exit_reason;
> +
> +       vm = vm_create_shape_with_one_vcpu(protected_vm_shape, &vcpu,
> +                                          guest_repeatedly_read);
> +
> +       /* Add a non-private memslot (flags = 0) */
> +       vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
> +                                   EXITS_TEST_GPA, EXITS_TEST_SLOT,
> +                                   EXITS_TEST_NPAGES, 0);
> +
> +       virt_map(vm, EXITS_TEST_GVA, EXITS_TEST_GPA, EXITS_TEST_NPAGES);
> +
> +       /* Request to access page privately */
> +       vm_mem_set_private(vm, EXITS_TEST_GPA, EXITS_TEST_SIZE);
> +
> +       exit_reason = run_vcpu_get_exit_reason(vcpu);
> +
> +       TEST_ASSERT_EQ(exit_reason, KVM_EXIT_MEMORY_FAULT);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.flags, KVM_MEMORY_EXIT_FLAG_PRIVATE);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.gpa, EXITS_TEST_GPA);
> +       TEST_ASSERT_EQ(vcpu->run->memory_fault.size, EXITS_TEST_SIZE);
> +
> +       kvm_vm_free(vm);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +       TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
> +
> +       test_private_access_memslot_deleted();
> +       test_private_access_memslot_not_private();
> +}
> --
> 2.39.1
>
>