KVM: selftests: Fix nx_huge_pages_test on TDP-disabled hosts

Map the test's huge page region with 2MiB virtual mappings when TDP is
disabled so that KVM can shadow the region with huge pages. This fixes
nx_huge_pages_test on hosts where TDP hardware support is disabled.

Purposely do not skip this test on TDP-disabled hosts. While we don't
care about NX Huge Pages on TDP-disabled hosts from a security
perspective, KVM does support it, and so we should test it.

For TDP-enabled hosts, continue mapping the region with 4KiB pages to
ensure that KVM can map it with huge pages irrespective of the guest
mappings.

Fixes: 8448ec5 ("KVM: selftests: Add NX huge pages test")
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220929181207.2281449-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -825,6 +825,8 @@ static inline uint8_t wrmsr_safe(uint32_t msr, uint64_t val)
 	return kvm_asm_safe("wrmsr", "a"(val & -1u), "d"(val >> 32), "c"(msr));
 }
 
+bool kvm_is_tdp_enabled(void);
+
 uint64_t vm_get_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
 				 uint64_t vaddr);
 void vm_set_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
@@ -855,6 +857,8 @@ enum pg_level {
 #define PG_SIZE_1G PG_LEVEL_SIZE(PG_LEVEL_1G)
 
 void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level);
+void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
+		    uint64_t nr_bytes, int level);
 
 /*
  * Basic CPU control in CR0

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -111,6 +111,14 @@ static void sregs_dump(FILE *stream, struct kvm_sregs *sregs, uint8_t indent)
 	}
 }
 
+bool kvm_is_tdp_enabled(void)
+{
+	if (is_intel_cpu())
+		return get_kvm_intel_param_bool("ept");
+	else
+		return get_kvm_amd_param_bool("npt");
+}
+
 void virt_arch_pgd_alloc(struct kvm_vm *vm)
 {
 	TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K, "Attempt to use "
@@ -214,6 +222,25 @@ void virt_arch_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
 	__virt_pg_map(vm, vaddr, paddr, PG_LEVEL_4K);
 }
 
+void virt_map_level(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
+		    uint64_t nr_bytes, int level)
+{
+	uint64_t pg_size = PG_LEVEL_SIZE(level);
+	uint64_t nr_pages = nr_bytes / pg_size;
+	int i;
+
+	TEST_ASSERT(nr_bytes % pg_size == 0,
+		    "Region size not aligned: nr_bytes: 0x%lx, page size: 0x%lx",
+		    nr_bytes, pg_size);
+
+	for (i = 0; i < nr_pages; i++) {
+		__virt_pg_map(vm, vaddr, paddr, level);
+
+		vaddr += pg_size;
+		paddr += pg_size;
+	}
+}
+
 static uint64_t *_vm_get_page_table_entry(struct kvm_vm *vm,
 					  struct kvm_vcpu *vcpu,
 					  uint64_t vaddr)

tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c

@@ -112,6 +112,7 @@ void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
 {
 	struct kvm_vcpu *vcpu;
 	struct kvm_vm *vm;
+	uint64_t nr_bytes;
 	void *hva;
 	int r;
 
@@ -141,10 +142,24 @@ void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
 				    HPAGE_GPA, HPAGE_SLOT,
 				    HPAGE_SLOT_NPAGES, 0);
 
-	virt_map(vm, HPAGE_GVA, HPAGE_GPA, HPAGE_SLOT_NPAGES);
+	nr_bytes = HPAGE_SLOT_NPAGES * vm->page_size;
+
+	/*
+	 * Ensure that KVM can map HPAGE_SLOT with huge pages by mapping the
+	 * region into the guest with 2MiB pages whenever TDP is disabled (i.e.
+	 * whenever KVM is shadowing the guest page tables).
+	 *
+	 * When TDP is enabled, KVM should be able to map HPAGE_SLOT with huge
+	 * pages irrespective of the guest page size, so map with 4KiB pages
+	 * to test that that is the case.
+	 */
+	if (kvm_is_tdp_enabled())
+		virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_4K);
+	else
+		virt_map_level(vm, HPAGE_GVA, HPAGE_GPA, nr_bytes, PG_LEVEL_2M);
 
 	hva = addr_gpa2hva(vm, HPAGE_GPA);
-	memset(hva, RETURN_OPCODE, HPAGE_SLOT_NPAGES * PAGE_SIZE);
+	memset(hva, RETURN_OPCODE, nr_bytes);
 
 	check_2m_page_count(vm, 0);
 	check_split_count(vm, 0);