[PATCH 5/5] KVM: selftests: Test protection of the ucall MMIO region

[Tharit Tangkijwanichakul <tharitt97@gmail.com>]

Verify that creating a memslot overlapping the ucall MMIO region
fails with EEXIST and that ucalls work before and after the
attempt. Skip when MMIO ucalls or read-only memory are unsupported.

Signed-off-by: Tharit Tangkijwanichakul <tharitt97@gmail.com>
---
 tools/testing/selftests/kvm/Makefile.kvm      |  1 +
 .../selftests/kvm/reserved_slot_test.c        | 61 +++++++++++++++++++
 2 files changed, 62 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/reserved_slot_test.c

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 1f4bc2a1322d..ff4a5e9733e9 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -68,6 +68,7 @@ TEST_GEN_PROGS_COMMON += set_memory_region_test
 TEST_GEN_PROGS_COMMON += memslot_modification_stress_test
 TEST_GEN_PROGS_COMMON += memslot_perf_test
 TEST_GEN_PROGS_COMMON += vm_types_test
+TEST_GEN_PROGS_COMMON += reserved_slot_test
 
 # Compiled test targets
 TEST_GEN_PROGS_x86 = $(TEST_GEN_PROGS_COMMON)
diff --git a/tools/testing/selftests/kvm/reserved_slot_test.c b/tools/testing/selftests/kvm/reserved_slot_test.c
new file mode 100644
index 000000000000..4a908017ca73
--- /dev/null
+++ b/tools/testing/selftests/kvm/reserved_slot_test.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "kvm_util.h"
+#include "processor.h"
+#include "test_util.h"
+
+#define CLOBBERED_SLOT		TEST_MEM_SLOT_BASE
+
+static void guest_code(void)
+{
+	GUEST_SYNC(1);
+	GUEST_SYNC(2);
+}
+
+static void test_slot1_protected(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_run *run;
+	struct kvm_vm *vm;
+	struct ucall uc;
+	u32 nr_pages;
+	size_t slot_size;
+	void *slot_mem;
+	int ret;
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+	nr_pages = vm_adjust_num_guest_pages(vm->mode, 1);
+	slot_size = (size_t)nr_pages * vm->page_size;
+
+	run = vcpu->run;
+	vcpu_run(vcpu);
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_MMIO,
+		    "Unexpected exit reason = %u", run->exit_reason);
+	TEST_ASSERT(get_ucall(vcpu, &uc) == UCALL_SYNC && uc.args[1] == 1,
+		    "Expected the first sync before clobbering the ucall GPA");
+
+	slot_mem = kvm_mmap(slot_size, PROT_READ | PROT_WRITE,
+			    MAP_PRIVATE | MAP_ANONYMOUS, -1);
+	ret = __vm_set_user_memory_region2(vm, CLOBBERED_SLOT, 0,
+					   vm->ucall_mmio_addr, slot_size, slot_mem, 0, 0);
+	TEST_ASSERT(ret == -1 && errno == EEXIST,
+		    "Expected the ucall GPA overlap to be rejected: ret=%d errno=%d",
+		    ret, errno);
+
+	vcpu_run(vcpu);
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_MMIO,
+		    "Unexpected exit reason = %u", run->exit_reason);
+	TEST_ASSERT(get_ucall(vcpu, &uc) == UCALL_SYNC && uc.args[1] == 2,
+		    "Expected the second sync after attempting to clobber the ucall GPA");
+
+	kvm_vm_free(vm);
+	TEST_ASSERT(!munmap(slot_mem, slot_size), "munmap() failed, errno=%d", errno);
+}
+
+int main(void)
+{
+	TEST_REQUIRE(UCALL_EXIT_REASON == KVM_EXIT_MMIO);
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_READONLY_MEM));
+
+	test_slot1_protected();
+	return 0;
+}
-- 
2.53.0