On 8/16/2024 2:23 PM, Pratik R. Sampat wrote:
> From: Michael Roth <michael.roth@xxxxxxx>
>
> SEV, SEV-ES, and SNP have a few corner cases where there is potential
> for KVM_PRE_FAULT_MEMORY to behave differently depending on when it is
> issued during initial guest setup. Exercising these various paths
> requires a bit more fine-grained control over when the
> KVM_PRE_FAULT_MEMORY requests are issued while setting up the guests.
>
> Since these CoCo-specific events are likely to be architecture-specific
> KST helpers, take the existing generic test in pre_fault_memory_test.c
> as a starting template, and then introduce an x86-specific version of
> it with expanded coverage for SEV, SEV-ES, and SNP.
>
> Since there's a reasonable chance that TDX could extend this for similar
> testing of TDX, give it a "coco-" prefix rather than an SEV-specific
> one.
>
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> Co-developed-by: Pratik R. Sampat <pratikrajesh.sampat@xxxxxxx>
> Signed-off-by: Pratik R. Sampat <pratikrajesh.sampat@xxxxxxx>
> ---
> tools/testing/selftests/kvm/Makefile | 1 +
> .../kvm/x86_64/coco_pre_fault_memory_test.c | 314 ++++++++++++++++++
> 2 files changed, 315 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/x86_64/coco_pre_fault_memory_test.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 48d32c5aa3eb..65d19b277b06 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -129,6 +129,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/amx_test
> TEST_GEN_PROGS_x86_64 += x86_64/max_vcpuid_cap_test
> TEST_GEN_PROGS_x86_64 += x86_64/triple_fault_event_test
> TEST_GEN_PROGS_x86_64 += x86_64/recalc_apic_map_test
> +TEST_GEN_PROGS_x86_64 += x86_64/coco_pre_fault_memory_test
> TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
> TEST_GEN_PROGS_x86_64 += demand_paging_test
> TEST_GEN_PROGS_x86_64 += dirty_log_test
> diff --git a/tools/testing/selftests/kvm/x86_64/coco_pre_fault_memory_test.c b/tools/testing/selftests/kvm/x86_64/coco_pre_fault_memory_test.c
> new file mode 100644
> index 000000000000..e16fe185fb5a
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/coco_pre_fault_memory_test.c
> @@ -0,0 +1,314 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/sizes.h>
> +
> +#include <test_util.h>
> +#include <kvm_util.h>
> +#include <processor.h>
> +#include "sev.h"
> +
> +/* Arbitrarily chosen values */
> +#define TEST_SIZE (SZ_2M + PAGE_SIZE)
> +#define TEST_NPAGES (TEST_SIZE / PAGE_SIZE)
> +#define TEST_SLOT 10
> +#define TEST_GPA 0x100000000ul
> +#define TEST_GVA 0x100000000ul
> +
> +enum prefault_snp_test_type {
> + /* Skip pre-faulting tests. */
> + NO_PREFAULT_TYPE = 0,
> + /*
> + * Issue KVM_PRE_FAULT_MEMORY for GFNs mapping non-private memory
> + * before finalizing the initial guest contents (e.g. via
> + * KVM_SEV_SNP_LAUNCH_FINISH for SNP guests).
> + *
> + * This should result in failure since KVM explicitly disallows
> + * KVM_PRE_FAULT_MEMORY from being issued prior to finalizing the
> + * initial guest contents.
> + */
> + PREFAULT_SHARED_BEFORE_FINALIZING = 0,
Just spotted that I have initialized both NO_PREFAULT_TYPE and
PREFAULT_SHARED_BEFORE_FINALIZING to 0, effectively running the latter
test type twice. I will fix in the next iteration that I post.
Thanks!
Pratik
> + /*
> + * Issue KVM_PRE_FAULT_MEMORY for GFNs mapping private memory
> + * before finalizing the initial guest contents (e.g. via
> + * KVM_SEV_SNP_LAUNCH_FINISH for SNP guests).
> + *
> + * This should result in failure since KVM explicitly disallows
> + * KVM_PRE_FAULT_MEMORY from being issued prior to finalizing the
> + * initial guest contents.
> + */
> + PREFAULT_PRIVATE_BEFORE_FINALIZING,
> + /*
> + * Issue KVM_PRE_FAULT_MEMORY for GFNs mapping shared/private
> + * memory after finalizing the initial guest contents
> + * (e.g. via * KVM_SEV_SNP_LAUNCH_FINISH for SNP guests).
> + *
> + * This should succeed since pre-faulting is supported for both
> + * non-private/private memory once the guest contents are finalized.
> + */
> + PREFAULT_PRIVATE_SHARED_AFTER_FINALIZING
> +};
> +
> +static void guest_code_sev(void)
> +{
> + int i;
> +
> + GUEST_ASSERT(rdmsr(MSR_AMD64_SEV) & MSR_AMD64_SEV_ENABLED);
> +
> + for (i = 0; i < TEST_NPAGES; i++) {
> + uint64_t *src = (uint64_t *)(TEST_GVA + i * PAGE_SIZE);
> + uint64_t val = *src;
> +
> + /* Validate the data stored in the pages */
> + if ((i < TEST_NPAGES / 2 && val != i + 1) ||
> + (i >= TEST_NPAGES / 2 && val != 0)) {
> + GUEST_FAIL("Inconsistent view of memory values in guest");
> + }
> + }
> +
> + if (rdmsr(MSR_AMD64_SEV) & MSR_AMD64_SEV_ES_ENABLED) {
> + wrmsr(MSR_AMD64_SEV_ES_GHCB, GHCB_MSR_TERM_REQ);
> + __asm__ __volatile__("rep; vmmcall");
> + GUEST_FAIL("This should be unreachable.");
> + }
> +
> + GUEST_DONE();
> +}
> +
> +static void __pre_fault_memory(struct kvm_vcpu *vcpu, u64 gpa, u64 size,
> + u64 left, bool expect_fail)
> +{
> + struct kvm_pre_fault_memory range = {
> + .gpa = gpa,
> + .size = size,
> + .flags = 0,
> + };
> + int ret, save_errno;
> + u64 prev;
> +
> + do {
> + prev = range.size;
> + ret = __vcpu_ioctl(vcpu, KVM_PRE_FAULT_MEMORY, &range);
> + save_errno = errno;
> + TEST_ASSERT((range.size < prev) ^ (ret < 0),
> + "%sexpecting range.size to change on %s",
> + ret < 0 ? "not " : "",
> + ret < 0 ? "failure" : "success");
> + } while (ret >= 0 ? range.size : save_errno == EINTR);
> +
> + TEST_ASSERT(expect_fail ? !(range.size == left) : (range.size == left),
> + "[EXPECT %s] completed with %lld bytes left, expected %" PRId64,
> + expect_fail ? "FAIL" : "PASS",
> + range.size, left);
> +
> + if (left == 0) {
> + TEST_ASSERT(expect_fail ? ret : !ret,
> + "[EXPECT %s] KVM_PRE_FAULT_MEMORY",
> + expect_fail ? "FAIL" : "PASS");
> + } else {
> + /*
> + * For shared memory, no memory slot causes RET_PF_EMULATE. It
> + * results in -ENOENT.
> + *
> + * For private memory, no memory slot is an error case returning
> + * -EFAULT, but it also possible the only the GPA ranges backed
> + * by a slot are marked as private, in which case the noslot
> + * range will also result in -ENOENT.
> + *
> + * So allow both errors for now, but in the future it would be
> + * good to distinguish between these cases to tighten up the
> + * error-checking.
> + */
> + TEST_ASSERT(expect_fail ? !ret :
> + (ret && (save_errno == EFAULT || save_errno == ENOENT)),
> + "[EXPECT %s] KVM_PRE_FAULT_MEMORY",
> + expect_fail ? "FAIL" : "PASS");
> + }
> +}
> +
> +static void pre_fault_memory(struct kvm_vcpu *vcpu, u64 gpa,
> + u64 size, u64 left)
> +{
> + __pre_fault_memory(vcpu, gpa, size, left, false);
> +}
> +
> +static void pre_fault_memory_negative(struct kvm_vcpu *vcpu, u64 gpa,
> + u64 size, u64 left)
> +{
> + __pre_fault_memory(vcpu, gpa, size, left, true);
> +}
> +
> +static void pre_fault_memory_snp(struct kvm_vcpu *vcpu, struct kvm_vm *vm,
> + bool private, enum prefault_snp_test_type p_type)
> +{
> + if (p_type == PREFAULT_SHARED_BEFORE_FINALIZING)
> + pre_fault_memory_negative(vcpu, TEST_GPA, SZ_2M, 0);
> +
> + snp_vm_launch_start(vm, SNP_POLICY);
> +
> + if (p_type == PREFAULT_SHARED_BEFORE_FINALIZING)
> + pre_fault_memory_negative(vcpu, TEST_GPA, SZ_2M, 0);
> +
> + if (private) {
> + /*
> + * Make sure when pages are pre-faulted later after
> + * finalization they are treated the same as a private
> + * access by the guest so that the expected gmem
> + * backing pages are used.
> + */
> + vm_mem_set_private(vm, TEST_GPA, TEST_SIZE);
> + if (p_type == PREFAULT_PRIVATE_BEFORE_FINALIZING)
> + pre_fault_memory_negative(vcpu, TEST_GPA, SZ_2M, 0);
> + } else {
> + if (p_type == PREFAULT_SHARED_BEFORE_FINALIZING)
> + pre_fault_memory_negative(vcpu, TEST_GPA, SZ_2M, 0);
> + }
> +
> + snp_vm_launch_update(vm);
> +
> + if (p_type == PREFAULT_SHARED_BEFORE_FINALIZING)
> + pre_fault_memory_negative(vcpu, TEST_GPA, SZ_2M, 0);
> +
> + snp_vm_launch_finish(vm);
> +
> + /*
> + * After finalization, pre-faulting either private or shared
> + * ranges should work regardless of whether the pages were
> + * encrypted as part of setting up initial guest state.
> + */
> + if (p_type == PREFAULT_PRIVATE_SHARED_AFTER_FINALIZING) {
> + pre_fault_memory(vcpu, TEST_GPA, SZ_2M, 0);
> + pre_fault_memory(vcpu, TEST_GPA + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
> + pre_fault_memory(vcpu, TEST_GPA + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
> + }
> +}
> +
> +static void pre_fault_memory_sev(unsigned long vm_type, struct kvm_vcpu *vcpu,
> + struct kvm_vm *vm)
> +{
> + uint32_t policy = (vm_type == KVM_X86_SEV_ES_VM) ? SEV_POLICY_ES : 0;
> +
> + pre_fault_memory(vcpu, TEST_GPA, SZ_2M, 0);
> + pre_fault_memory(vcpu, TEST_GPA + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
> + pre_fault_memory(vcpu, TEST_GPA + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
> +
> + sev_vm_launch(vm, policy);
> +
> + pre_fault_memory(vcpu, TEST_GPA, SZ_2M, 0);
> + pre_fault_memory(vcpu, TEST_GPA + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
> + pre_fault_memory(vcpu, TEST_GPA + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
> +
> + sev_vm_launch_measure(vm, alloca(256));
> +
> + pre_fault_memory(vcpu, TEST_GPA, SZ_2M, 0);
> + pre_fault_memory(vcpu, TEST_GPA + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
> + pre_fault_memory(vcpu, TEST_GPA + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
> +
> + sev_vm_launch_finish(vm);
> +
> + pre_fault_memory(vcpu, TEST_GPA, SZ_2M, 0);
> + pre_fault_memory(vcpu, TEST_GPA + SZ_2M, PAGE_SIZE * 2, PAGE_SIZE);
> + pre_fault_memory(vcpu, TEST_GPA + TEST_SIZE, PAGE_SIZE, PAGE_SIZE);
> +}
> +
> +static void test_pre_fault_memory_sev(unsigned long vm_type, bool private,
> + enum prefault_snp_test_type p_type)
> +{
> + struct kvm_vcpu *vcpu;
> + struct kvm_vm *vm;
> + struct ucall uc;
> + int i;
> +
> + vm = vm_sev_create_with_one_vcpu(vm_type, guest_code_sev, &vcpu);
> +
> + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
> + TEST_GPA, TEST_SLOT, TEST_NPAGES,
> + (vm_type == KVM_X86_SNP_VM) ? KVM_MEM_GUEST_MEMFD : 0);
> +
> + /*
> + * Make sure guest page table is in agreement with what pages will be
> + * initially encrypted by the ASP.
> + */
> + if (private)
> + vm_mem_set_protected(vm, TEST_SLOT, TEST_GPA, TEST_NPAGES);
> +
> + virt_map(vm, TEST_GVA, TEST_GPA, TEST_NPAGES);
> +
> + /*
> + * Populate the pages to compare data read from the guest
> + * Populate the first half with data and second half as all zeros.
> + */
> + for (i = 0; i < TEST_NPAGES; i++) {
> + uint64_t *hva = addr_gva2hva(vm, TEST_GVA + i * PAGE_SIZE);
> +
> + if (i < TEST_NPAGES / 2)
> + *hva = i + 1;
> + else
> + *hva = 0;
> + }
> +
> + if (vm_type == KVM_X86_SNP_VM)
> + pre_fault_memory_snp(vcpu, vm, private, p_type);
> + else
> + pre_fault_memory_sev(vm_type, vcpu, vm);
> +
> + vcpu_run(vcpu);
> +
> + if (vm->type == KVM_X86_SEV_ES_VM || vm->type == KVM_X86_SNP_VM) {
> + TEST_ASSERT(vcpu->run->exit_reason == KVM_EXIT_SYSTEM_EVENT,
> + "Wanted SYSTEM_EVENT, got %s",
> + exit_reason_str(vcpu->run->exit_reason));
> + TEST_ASSERT_EQ(vcpu->run->system_event.type, KVM_SYSTEM_EVENT_SEV_TERM);
> + TEST_ASSERT_EQ(vcpu->run->system_event.ndata, 1);
> + TEST_ASSERT_EQ(vcpu->run->system_event.data[0], GHCB_MSR_TERM_REQ);
> + goto out;
> + }
> +
> + switch (get_ucall(vcpu, &uc)) {
> + case UCALL_DONE:
> + break;
> + case UCALL_ABORT:
> + REPORT_GUEST_ASSERT(uc);
> + default:
> + TEST_FAIL("Unexpected exit: %s",
> + exit_reason_str(vcpu->run->exit_reason));
> + }
> +
> +out:
> + kvm_vm_free(vm);
> +}
> +
> +static void test_pre_fault_memory(unsigned long vm_type, bool private)
> +{
> + int pt;
> +
> + if (vm_type && !(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(vm_type))) {
> + pr_info("Skipping tests for vm_type 0x%lx\n", vm_type);
> + return;
> + }
> +
> + switch (vm_type) {
> + case KVM_X86_SEV_VM:
> + case KVM_X86_SEV_ES_VM:
> + test_pre_fault_memory_sev(vm_type, private, NO_PREFAULT_TYPE);
> + break;
> + case KVM_X86_SNP_VM:
> + for (pt = 0; pt <= PREFAULT_PRIVATE_SHARED_AFTER_FINALIZING; pt++)
> + test_pre_fault_memory_sev(vm_type, private, pt);
> + break;
> + default:
> + abort();
> + }
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + TEST_REQUIRE(kvm_check_cap(KVM_CAP_PRE_FAULT_MEMORY));
> +
> + test_pre_fault_memory(KVM_X86_SEV_VM, false);
> + test_pre_fault_memory(KVM_X86_SEV_VM, true);
> + test_pre_fault_memory(KVM_X86_SEV_ES_VM, false);
> + test_pre_fault_memory(KVM_X86_SEV_ES_VM, true);
> + test_pre_fault_memory(KVM_X86_SNP_VM, false);
> + test_pre_fault_memory(KVM_X86_SNP_VM, true);
> +
> + return 0;
> +}
