Re: [PATCH RFC v4 25/44] KVM: selftests: Test basic single-page conversion flow

[Ackerley Tng <ackerleytng@google.com>]

Ackerley Tng <ackerleytng@google.com> writes:

> Add a selftest for the guest_memfd memory attribute conversion ioctls.
> The test starts the guest_memfd as all-private (the default state), and
> verifies the basic flow of converting a single page to shared and then back
> to private.
>
> Add infrastructure that supports extensions to other conversion flow
> tests. This infrastructure will be used in upcoming patches for other
> conversion tests.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Co-developed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  tools/testing/selftests/kvm/Makefile.kvm           |   1 +
>  .../selftests/kvm/guest_memfd_conversions_test.c   | 205 +++++++++++++++++++++
>  2 files changed, 206 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> index dc68371f76a33..0e2a9adfca57e 100644
> --- a/tools/testing/selftests/kvm/Makefile.kvm
> +++ b/tools/testing/selftests/kvm/Makefile.kvm
> @@ -147,6 +147,7 @@ TEST_GEN_PROGS_x86 += access_tracking_perf_test
>  TEST_GEN_PROGS_x86 += coalesced_io_test
>  TEST_GEN_PROGS_x86 += dirty_log_perf_test
>  TEST_GEN_PROGS_x86 += guest_memfd_test
> +TEST_GEN_PROGS_x86 += guest_memfd_conversions_test
>  TEST_GEN_PROGS_x86 += hardware_disable_test
>  TEST_GEN_PROGS_x86 += memslot_modification_stress_test
>  TEST_GEN_PROGS_x86 += memslot_perf_test
> diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
> new file mode 100644
> index 0000000000000..841b2824ae996
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
> @@ -0,0 +1,205 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2024, Google LLC.
> + */
> +#include <sys/mman.h>
> +#include <unistd.h>
> +
> +#include <linux/align.h>
> +#include <linux/kvm.h>
> +#include <linux/sizes.h>
> +
> +#include "kvm_util.h"
> +#include "kselftest_harness.h"
> +#include "test_util.h"
> +#include "ucall_common.h"
> +
> +FIXTURE(gmem_conversions) {
> +	struct kvm_vcpu *vcpu;
> +	int gmem_fd;
> +	/* HVA of the first byte of the memory mmap()-ed from gmem_fd. */
> +	char *mem;
> +};
> +
> +typedef FIXTURE_DATA(gmem_conversions) test_data_t;
> +
> +FIXTURE_SETUP(gmem_conversions) { }
> +
> +static uint64_t page_size;
> +
> +static void guest_do_rmw(void);
> +#define GUEST_MEMFD_SHARING_TEST_GVA 0x90000000ULL
> +
> +/*
> + * Defer setup until the individual test is invoked so that tests can specify
> + * the number of pages and flags for the guest_memfd instance.
> + */
> +static void gmem_conversions_do_setup(test_data_t *t, int nr_pages,
> +				      int gmem_flags)
> +{
> +	const struct vm_shape shape = {
> +		.mode = VM_MODE_DEFAULT,
> +		.type = KVM_X86_SW_PROTECTED_VM,
> +	};
> +	/*
> +	 * Use high GPA above APIC_DEFAULT_PHYS_BASE to avoid clashing with
> +	 * APIC_DEFAULT_PHYS_BASE.
> +	 */
> +	const uint64_t gpa = SZ_4G;
> +	const uint32_t slot = 1;
> +	u64 supported_flags;
> +	struct kvm_vm *vm;
> +
> +	vm = __vm_create_shape_with_one_vcpu(shape, &t->vcpu, nr_pages, guest_do_rmw);
> +
> +	supported_flags = vm_check_cap(vm, KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS);
> +	TEST_REQUIRE(supported_flags & KVM_SET_MEMORY_ATTRIBUTES2_PRESERVE);
> +
> +	vm_mem_add(vm, VM_MEM_SRC_SHMEM, gpa, slot, nr_pages,
> +		   KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);
> +
> +	t->gmem_fd = kvm_slot_to_fd(vm, slot);
> +	t->mem = addr_gpa2hva(vm, gpa);
> +	virt_map(vm, GUEST_MEMFD_SHARING_TEST_GVA, gpa, nr_pages);
> +}
> +
> +static void gmem_conversions_do_teardown(test_data_t *t)
> +{
> +	/* No need to close gmem_fd, it's owned by the VM structure. */
> +	kvm_vm_free(t->vcpu->vm);
> +}
> +
> +FIXTURE_TEARDOWN(gmem_conversions)
> +{
> +	gmem_conversions_do_teardown(self);
> +}
> +
> +/*
> + * In these test definition macros, __nr_pages and nr_pages is used to set up
> + * the total number of pages in the guest_memfd under test. This will be
> + * available in the test definitions as nr_pages.
> + */
> +
> +#define __GMEM_CONVERSION_TEST(test, __nr_pages, flags)				\
> +static void __gmem_conversions_##test(test_data_t *t, int nr_pages);		\
> +										\
> +TEST_F(gmem_conversions, test)							\
> +{										\
> +	gmem_conversions_do_setup(self, __nr_pages, flags);			\
> +	__gmem_conversions_##test(self, __nr_pages);				\
> +}										\
> +static void __gmem_conversions_##test(test_data_t *t, int nr_pages)		\
> +
> +#define GMEM_CONVERSION_TEST(test, __nr_pages, flags)				\
> +	__GMEM_CONVERSION_TEST(test, __nr_pages, (flags) | GUEST_MEMFD_FLAG_MMAP)
> +
> +#define __GMEM_CONVERSION_TEST_INIT_PRIVATE(test, __nr_pages)			\
> +	GMEM_CONVERSION_TEST(test, __nr_pages, 0)
> +
> +#define GMEM_CONVERSION_TEST_INIT_PRIVATE(test)					\
> +	__GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
> +
> +struct guest_check_data {
> +	void *mem;
> +	char expected_val;
> +	char write_val;
> +};
> +static struct guest_check_data guest_data;
> +
> +static void guest_do_rmw(void)
> +{
> +	for (;;) {
> +		char *mem = READ_ONCE(guest_data.mem);
> +
> +		GUEST_ASSERT_EQ(READ_ONCE(*mem), READ_ONCE(guest_data.expected_val));
> +		WRITE_ONCE(*mem, READ_ONCE(guest_data.write_val));
> +
> +		GUEST_SYNC(0);
> +	}
> +}
> +
> +static void run_guest_do_rmw(struct kvm_vcpu *vcpu, loff_t pgoff,
> +			     char expected_val, char write_val)
> +{
> +	struct ucall uc;
> +	int r;
> +
> +	guest_data.mem = (void *)GUEST_MEMFD_SHARING_TEST_GVA + pgoff * page_size;
> +	guest_data.expected_val = expected_val;
> +	guest_data.write_val = write_val;
> +	sync_global_to_guest(vcpu->vm, guest_data);
> +
> +	do {
> +		r = __vcpu_run(vcpu);
> +	} while (r == -1 && errno == EINTR);
> +
> +	TEST_ASSERT_EQ(r, 0);

TEST_ASSERT_EQ() ends up calling exit() on failures, which skips
FIXTURE_TEARDOWN().

Other than the explicit assertions not working with the
kselftest_harness, kvm selftest library functions like vm_mem_add() also
call TEST_ASSERT, which doesn't play nice with kselftest_harness.

Any suggestions for this? Should we use the kselftest framework with
these tests?

(I ran into this issue while trying to test something else, where I
needed FIXTURE_TEARDOWN() to clean up system state.)

Or is it "okay" in this case since FIXTURE_TEARDOWN() only cleans up
stuff that would happen if the program exits anyway?

>
> [...snip...]
>