Re: [RFC PATCH v5 28/29] KVM: selftests: TDX: Add TDX UPM selftest

[Yan Zhao]

On Tue, Dec 12, 2023 at 12:46:43PM -0800, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> 
> This tests the use of guest memory with explicit MapGPA calls.
> 
> Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Signed-off-by: Ryan Afranji <afranji@xxxxxxxxxx>
> Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/x86_64/tdx_upm_test.c       | 401 ++++++++++++++++++
>  2 files changed, 402 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/x86_64/tdx_upm_test.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 8c0a6b395ee5..2f2669af15d6 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -157,6 +157,7 @@ TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
>  TEST_GEN_PROGS_x86_64 += system_counter_offset_test
>  TEST_GEN_PROGS_x86_64 += x86_64/tdx_vm_tests
>  TEST_GEN_PROGS_x86_64 += x86_64/tdx_shared_mem_test
> +TEST_GEN_PROGS_x86_64 += x86_64/tdx_upm_test
>  
>  # Compiled outputs used by test targets
>  TEST_GEN_PROGS_EXTENDED_x86_64 += x86_64/nx_huge_pages_test
> diff --git a/tools/testing/selftests/kvm/x86_64/tdx_upm_test.c b/tools/testing/selftests/kvm/x86_64/tdx_upm_test.c
> new file mode 100644
> index 000000000000..44671874a4f1
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/tdx_upm_test.c
> @@ -0,0 +1,401 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <asm/kvm.h>
> +#include <asm/vmx.h>
> +#include <linux/kvm.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +
> +#include "kvm_util_base.h"
> +#include "processor.h"
> +#include "tdx/tdcall.h"
> +#include "tdx/tdx.h"
> +#include "tdx/tdx_util.h"
> +#include "tdx/test_util.h"
> +#include "test_util.h"
> +
> +/* TDX UPM test patterns */
> +#define PATTERN_CONFIDENCE_CHECK (0x11)
> +#define PATTERN_HOST_FOCUS (0x22)
> +#define PATTERN_GUEST_GENERAL (0x33)
> +#define PATTERN_GUEST_FOCUS (0x44)
> +
> +/*
> + * 0x80000000 is arbitrarily selected. The selected address need not be the same
> + * as TDX_UPM_TEST_AREA_GVA_PRIVATE, but it should not overlap with selftest
> + * code or boot page.
> + */
> +#define TDX_UPM_TEST_AREA_GPA (0x80000000)
> +/* Test area GPA is arbitrarily selected */
> +#define TDX_UPM_TEST_AREA_GVA_PRIVATE (0x90000000)
> +/* Select any bit that can be used as a flag */
> +#define TDX_UPM_TEST_AREA_GVA_SHARED_BIT (32)
> +/*
> + * TDX_UPM_TEST_AREA_GVA_SHARED is used to map the same GPA twice into the
> + * guest, once as shared and once as private
> + */
> +#define TDX_UPM_TEST_AREA_GVA_SHARED				\
> +	(TDX_UPM_TEST_AREA_GVA_PRIVATE |			\
> +		BIT_ULL(TDX_UPM_TEST_AREA_GVA_SHARED_BIT))
> +
> +/* The test area is 2MB in size */
> +#define TDX_UPM_TEST_AREA_SIZE (2 << 20)
> +/* 0th general area is 1MB in size */
> +#define TDX_UPM_GENERAL_AREA_0_SIZE (1 << 20)
> +/* Focus area is 40KB in size */
> +#define TDX_UPM_FOCUS_AREA_SIZE (40 << 10)
> +/* 1st general area is the rest of the space in the test area */
> +#define TDX_UPM_GENERAL_AREA_1_SIZE				\
> +	(TDX_UPM_TEST_AREA_SIZE - TDX_UPM_GENERAL_AREA_0_SIZE -	\
> +		TDX_UPM_FOCUS_AREA_SIZE)
> +
> +/*
> + * The test memory area is set up as two general areas, sandwiching a focus
> + * area.  The general areas act as control areas. After they are filled, they
> + * are not expected to change throughout the tests. The focus area is memory
> + * permissions change from private to shared and vice-versa.
> + *
> + * The focus area is intentionally small, and sandwiched to test that when the
> + * focus area's permissions change, the other areas' permissions are not
> + * affected.
> + */
> +struct __packed tdx_upm_test_area {
> +	uint8_t general_area_0[TDX_UPM_GENERAL_AREA_0_SIZE];
> +	uint8_t focus_area[TDX_UPM_FOCUS_AREA_SIZE];
> +	uint8_t general_area_1[TDX_UPM_GENERAL_AREA_1_SIZE];
> +};
> +
> +static void fill_test_area(struct tdx_upm_test_area *test_area_base,
> +			uint8_t pattern)
> +{
> +	memset(test_area_base, pattern, sizeof(*test_area_base));
> +}
> +
> +static void fill_focus_area(struct tdx_upm_test_area *test_area_base,
> +			    uint8_t pattern)
> +{
> +	memset(test_area_base->focus_area, pattern,
> +	       sizeof(test_area_base->focus_area));
> +}
> +
> +static bool check_area(uint8_t *base, uint64_t size, uint8_t expected_pattern)
> +{
> +	size_t i;
> +
> +	for (i = 0; i < size; i++) {
> +		if (base[i] != expected_pattern)
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
> +static bool check_general_areas(struct tdx_upm_test_area *test_area_base,
> +				uint8_t expected_pattern)
> +{
> +	return (check_area(test_area_base->general_area_0,
> +			   sizeof(test_area_base->general_area_0),
> +			   expected_pattern) &&
> +		check_area(test_area_base->general_area_1,
> +			   sizeof(test_area_base->general_area_1),
> +			   expected_pattern));
> +}
> +
> +static bool check_focus_area(struct tdx_upm_test_area *test_area_base,
> +			     uint8_t expected_pattern)
> +{
> +	return check_area(test_area_base->focus_area,
> +			  sizeof(test_area_base->focus_area), expected_pattern);
> +}
> +
> +static bool check_test_area(struct tdx_upm_test_area *test_area_base,
> +			    uint8_t expected_pattern)
> +{
> +	return (check_general_areas(test_area_base, expected_pattern) &&
> +		check_focus_area(test_area_base, expected_pattern));
> +}
> +
> +static bool fill_and_check(struct tdx_upm_test_area *test_area_base, uint8_t pattern)
> +{
> +	fill_test_area(test_area_base, pattern);
> +
> +	return check_test_area(test_area_base, pattern);
> +}
> +
> +#define TDX_UPM_TEST_ASSERT(x)				\
> +	do {						\
> +		if (!(x))				\
> +			tdx_test_fatal(__LINE__);	\
> +	} while (0)
> +
> +/*
> + * Shared variables between guest and host
> + */
> +static struct tdx_upm_test_area *test_area_gpa_private;
> +static struct tdx_upm_test_area *test_area_gpa_shared;
> +
> +/*
> + * Test stages for syncing with host
> + */
> +enum {
> +	SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST = 1,
> +	SYNC_CHECK_READ_SHARED_MEMORY_FROM_HOST,
> +	SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST_AGAIN,
> +};
> +
> +#define TDX_UPM_TEST_ACCEPT_PRINT_PORT 0x87
> +
> +/**
> + * Does vcpu_run, and also manages memory conversions if requested by the TD.
> + */
> +void vcpu_run_and_manage_memory_conversions(struct kvm_vm *vm,
> +					    struct kvm_vcpu *vcpu)
> +{
> +	for (;;) {
> +		vcpu_run(vcpu);
> +		if (vcpu->run->exit_reason == KVM_EXIT_TDX &&
> +			vcpu->run->tdx.type == KVM_EXIT_TDX_VMCALL &&
> +			vcpu->run->tdx.u.vmcall.subfunction == TDG_VP_VMCALL_MAP_GPA) {
> +			struct kvm_tdx_vmcall *vmcall_info = &vcpu->run->tdx.u.vmcall;
> +			uint64_t gpa = vmcall_info->in_r12 & ~vm->arch.s_bit;
> +
> +			handle_memory_conversion(vm, gpa, vmcall_info->in_r13,
> +				!(vm->arch.s_bit & vmcall_info->in_r12));
> +			vmcall_info->status_code = 0;
> +			continue;
> +		} else if (
> +			vcpu->run->exit_reason == KVM_EXIT_IO &&
> +			vcpu->run->io.port == TDX_UPM_TEST_ACCEPT_PRINT_PORT) {
> +			uint64_t gpa = tdx_test_read_64bit(
> +				vcpu, TDX_UPM_TEST_ACCEPT_PRINT_PORT);
> +			printf("\t ... guest accepting 1 page at GPA: 0x%lx\n", gpa);
> +			continue;
> +		}
> 
Lack of converting TDG_VP_VMCALL_REPORT_FATAL_ERROR to KVM_EXIT_SYSTEM_EVENT.

> +		break;
> +	}
> +}
> +
> +static void guest_upm_explicit(void)
> +{
> +	uint64_t ret = 0;
> +	uint64_t failed_gpa;
> +
> +	struct tdx_upm_test_area *test_area_gva_private =
> +		(struct tdx_upm_test_area *)TDX_UPM_TEST_AREA_GVA_PRIVATE;
> +	struct tdx_upm_test_area *test_area_gva_shared =
> +		(struct tdx_upm_test_area *)TDX_UPM_TEST_AREA_GVA_SHARED;
> +
> +	/* Check: host reading private memory does not modify guest's view */
> +	fill_test_area(test_area_gva_private, PATTERN_GUEST_GENERAL);
> +
> +	tdx_test_report_to_user_space(SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST);
> +
> +	TDX_UPM_TEST_ASSERT(
> +		check_test_area(test_area_gva_private, PATTERN_GUEST_GENERAL));
> +
> +	/* Remap focus area as shared */
> +	ret = tdg_vp_vmcall_map_gpa((uint64_t)test_area_gpa_shared->focus_area,
> +				    sizeof(test_area_gpa_shared->focus_area),
> +				    &failed_gpa);
"failed gpa" is not filled by host and is uninitialized.


> +	TDX_UPM_TEST_ASSERT(!ret);
> +
> +	/* General areas should be unaffected by remapping */
> +	TDX_UPM_TEST_ASSERT(
> +		check_general_areas(test_area_gva_private, PATTERN_GUEST_GENERAL));
> +
> +	/*
> +	 * Use memory contents to confirm that the memory allocated using mmap
> +	 * is used as backing memory for shared memory - PATTERN_CONFIDENCE_CHECK
> +	 * was written by the VMM at the beginning of this test.
> +	 */
> +	TDX_UPM_TEST_ASSERT(
> +		check_focus_area(test_area_gva_shared, PATTERN_CONFIDENCE_CHECK));
> +
> +	/* Guest can use focus area after remapping as shared */
> +	fill_focus_area(test_area_gva_shared, PATTERN_GUEST_FOCUS);
> +
> +	tdx_test_report_to_user_space(SYNC_CHECK_READ_SHARED_MEMORY_FROM_HOST);
> +
> +	/* Check that guest has the same view of shared memory */
> +	TDX_UPM_TEST_ASSERT(
> +		check_focus_area(test_area_gva_shared, PATTERN_HOST_FOCUS));
> +
> +	/* Remap focus area back to private */
> +	ret = tdg_vp_vmcall_map_gpa((uint64_t)test_area_gpa_private->focus_area,
> +				    sizeof(test_area_gpa_private->focus_area),
> +				    &failed_gpa);
> +	TDX_UPM_TEST_ASSERT(!ret);
> +
> +	/* General areas should be unaffected by remapping */
> +	TDX_UPM_TEST_ASSERT(
> +		check_general_areas(test_area_gva_private, PATTERN_GUEST_GENERAL));
> +
> +	/* Focus area should be zeroed after remapping */
> +	TDX_UPM_TEST_ASSERT(check_focus_area(test_area_gva_private, 0));
> +
> +	tdx_test_report_to_user_space(SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST_AGAIN);
> +
> +	/* Check that guest can use private memory after focus area is remapped as private */
> +	TDX_UPM_TEST_ASSERT(
> +		fill_and_check(test_area_gva_private, PATTERN_GUEST_GENERAL));
> +
> +	tdx_test_success();
> +}
> +
> +static void run_selftest(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
> +			 struct tdx_upm_test_area *test_area_base_hva)
> +{
> +	vcpu_run(vcpu);
Should be td_vcpu_run()?
Otherwise, nowhere to convert TDG_VP_VMCALL_REPORT_FATAL_ERROR to
exit_reason KVM_EXIT_SYSTEM_EVENT required by TDX_TEST_CHECK_GUEST_FAILURE().

> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_IO(vcpu, TDX_TEST_REPORT_PORT, TDX_TEST_REPORT_SIZE,
> +		 TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> +	TEST_ASSERT_EQ(*(uint32_t *)((void *)vcpu->run + vcpu->run->io.data_offset),
> +		  SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST);
> +
> +	/*
> +	 * Check that host should read PATTERN_CONFIDENCE_CHECK from guest's
> +	 * private memory. This confirms that regular memory (userspace_addr in
> +	 * struct kvm_userspace_memory_region) is used to back the host's view
> +	 * of private memory, since PATTERN_CONFIDENCE_CHECK was written to that
> +	 * memory before starting the guest.
> +	 */
> +	TEST_ASSERT(check_test_area(test_area_base_hva, PATTERN_CONFIDENCE_CHECK),
> +		"Host should read PATTERN_CONFIDENCE_CHECK from guest's private memory.");
> +
> +	vcpu_run_and_manage_memory_conversions(vm, vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_IO(vcpu, TDX_TEST_REPORT_PORT, TDX_TEST_REPORT_SIZE,
> +		 TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> +	TEST_ASSERT_EQ(*(uint32_t *)((void *)vcpu->run + vcpu->run->io.data_offset),
> +		  SYNC_CHECK_READ_SHARED_MEMORY_FROM_HOST);
> +
> +	TEST_ASSERT(check_focus_area(test_area_base_hva, PATTERN_GUEST_FOCUS),
> +		"Host should have the same view of shared memory as guest.");
> +	TEST_ASSERT(check_general_areas(test_area_base_hva, PATTERN_CONFIDENCE_CHECK),
> +		"Host's view of private memory should still be backed by regular memory.");
> +
> +	/* Check that host can use shared memory */
> +	fill_focus_area(test_area_base_hva, PATTERN_HOST_FOCUS);
> +	TEST_ASSERT(check_focus_area(test_area_base_hva, PATTERN_HOST_FOCUS),
> +		    "Host should be able to use shared memory.");
> +
> +	vcpu_run_and_manage_memory_conversions(vm, vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_IO(vcpu, TDX_TEST_REPORT_PORT, TDX_TEST_REPORT_SIZE,
> +		 TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> +	TEST_ASSERT_EQ(*(uint32_t *)((void *)vcpu->run + vcpu->run->io.data_offset),
> +		  SYNC_CHECK_READ_PRIVATE_MEMORY_FROM_HOST_AGAIN);
> +
> +	TEST_ASSERT(check_general_areas(test_area_base_hva, PATTERN_CONFIDENCE_CHECK),
> +		"Host's view of private memory should be backed by regular memory.");
> +	TEST_ASSERT(check_focus_area(test_area_base_hva, PATTERN_HOST_FOCUS),
> +		"Host's view of private memory should be backed by regular memory.");
> +
> +	vcpu_run(vcpu);
> +	TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> +	TDX_TEST_ASSERT_SUCCESS(vcpu);
> +
> +	printf("\t ... PASSED\n");
> +}
> +
> +static bool address_between(uint64_t addr, void *lo, void *hi)
> +{
> +	return (uint64_t)lo <= addr && addr < (uint64_t)hi;
> +}
> +
> +static void guest_ve_handler(struct ex_regs *regs)
> +{
> +	uint64_t ret;
> +	struct ve_info ve;
> +
> +	ret = tdg_vp_veinfo_get(&ve);
> +	TDX_UPM_TEST_ASSERT(!ret);
> +
> +	/* For this test, we will only handle EXIT_REASON_EPT_VIOLATION */
> +	TDX_UPM_TEST_ASSERT(ve.exit_reason == EXIT_REASON_EPT_VIOLATION);
> +
> +	/* Validate GPA in fault */
> +	TDX_UPM_TEST_ASSERT(
> +		address_between(ve.gpa,
> +				test_area_gpa_private->focus_area,
> +				test_area_gpa_private->general_area_1));
> +
> +	tdx_test_send_64bit(TDX_UPM_TEST_ACCEPT_PRINT_PORT, ve.gpa);
> +
> +#define MEM_PAGE_ACCEPT_LEVEL_4K 0
> +#define MEM_PAGE_ACCEPT_LEVEL_2M 1
> +	ret = tdg_mem_page_accept(ve.gpa, MEM_PAGE_ACCEPT_LEVEL_4K);
What if ve.gpa could end with 1?
e.g. if could be 0x80100001 if guest accesses test_area_gva_private->focus_area[1]
after remapping focus area back to private.

Though this does not happen in current test, it's better to strip the low 12
bits of ve.gpa before passing to tdg_mem_page_accept(),

> +	TDX_UPM_TEST_ASSERT(!ret);
> +}
> +
> +static void verify_upm_test(void)
> +{
> +	struct kvm_vm *vm;
> +	struct kvm_vcpu *vcpu;
> +
> +	vm_vaddr_t test_area_gva_private;
> +	struct tdx_upm_test_area *test_area_base_hva;
> +	uint64_t test_area_npages;
> +
> +	vm = td_create();
> +	td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> +	vcpu = td_vcpu_add(vm, 0, guest_upm_explicit);
> +
> +	vm_install_exception_handler(vm, VE_VECTOR, guest_ve_handler);
> +
> +	/*
> +	 * Set up shared memory page for testing by first allocating as private
> +	 * and then mapping the same GPA again as shared. This way, the TD does
> +	 * not have to remap its page tables at runtime.
> +	 */
> +	test_area_npages = TDX_UPM_TEST_AREA_SIZE / vm->page_size;
> +	vm_userspace_mem_region_add(vm,
> +				    VM_MEM_SRC_ANONYMOUS, TDX_UPM_TEST_AREA_GPA,
> +				    3, test_area_npages, KVM_MEM_PRIVATE);
> +
> +	test_area_gva_private = ____vm_vaddr_alloc(
> +		vm, TDX_UPM_TEST_AREA_SIZE, TDX_UPM_TEST_AREA_GVA_PRIVATE,
> +		TDX_UPM_TEST_AREA_GPA, 3, true);
> +	TEST_ASSERT_EQ(test_area_gva_private, TDX_UPM_TEST_AREA_GVA_PRIVATE);
> +
> +	test_area_gpa_private = (struct tdx_upm_test_area *)
> +		addr_gva2gpa(vm, test_area_gva_private);
> +	virt_map_shared(vm, TDX_UPM_TEST_AREA_GVA_SHARED,
> +			(uint64_t)test_area_gpa_private,
> +			test_area_npages);
> +	TEST_ASSERT_EQ(addr_gva2gpa(vm, TDX_UPM_TEST_AREA_GVA_SHARED),
> +		  (vm_paddr_t)test_area_gpa_private);
> +
> +	test_area_base_hva = addr_gva2hva(vm, TDX_UPM_TEST_AREA_GVA_PRIVATE);
> +
> +	TEST_ASSERT(fill_and_check(test_area_base_hva, PATTERN_CONFIDENCE_CHECK),
> +		"Failed to mark memory intended as backing memory for TD shared memory");
> +
> +	sync_global_to_guest(vm, test_area_gpa_private);
> +	test_area_gpa_shared = (struct tdx_upm_test_area *)
> +		((uint64_t)test_area_gpa_private | BIT_ULL(vm->pa_bits - 1));
> +	sync_global_to_guest(vm, test_area_gpa_shared);
> +
> +	td_finalize(vm);
> +
> +	printf("Verifying UPM functionality: explicit MapGPA\n");
> +
> +	run_selftest(vm, vcpu, test_area_base_hva);
> +
> +	kvm_vm_free(vm);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	/* Disable stdout buffering */
> +	setbuf(stdout, NULL);
> +
> +	if (!is_tdx_enabled()) {
> +		printf("TDX is not supported by the KVM\n"
> +		       "Skipping the TDX tests.\n");
> +		return 0;
> +	}
> +
> +	run_in_new_process(&verify_upm_test);
> +}
> -- 
> 2.43.0.472.g3155946c3a-goog
> 
>