KVM: selftests: Move setting a vCPU's entry point to a dedicated API

Extract the code to set a vCPU's entry point out of vm_arch_vcpu_add() and
into a new API, vcpu_arch_set_entry_point().  Providing a separate API
will allow creating a KVM selftests hardness that can handle tests that
use different entry points for sub-tests, whereas *requiring* the entry
point to be specified at vCPU creation makes it difficult to create a
generic harness, e.g. the boilerplate setup/teardown can't easily create
and destroy the VM and vCPUs.
Signed-off-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20240208204844.119326-4-thuth@redhat.comSigned-off-by: Sean Christopherson <seanjc@google.com>

tools/testing/selftests/kvm/include/kvm_util_base.h

@@ -969,15 +969,18 @@ static inline void vcpu_dump(FILE *stream, struct kvm_vcpu *vcpu,
  * Input Args:
  *   vm - Virtual Machine
  *   vcpu_id - The id of the VCPU to add to the VM.
- *   guest_code - The vCPU's entry point
  */
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  void *guest_code);
+struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id);
+void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code);
 
 static inline struct kvm_vcpu *vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 					   void *guest_code)
 {
-	return vm_arch_vcpu_add(vm, vcpu_id, guest_code);
+	struct kvm_vcpu *vcpu = vm_arch_vcpu_add(vm, vcpu_id);
+
+	vcpu_arch_set_entry_point(vcpu, guest_code);
+
+	return vcpu;
 }
 
 /* Re-create a vCPU after restarting a VM, e.g. for state save/restore tests. */

tools/testing/selftests/kvm/lib/aarch64/processor.c

@@ -365,8 +365,13 @@ void vcpu_arch_dump(FILE *stream, struct kvm_vcpu *vcpu, uint8_t indent)
 		indent, "", pstate, pc);
 }
 
-struct kvm_vcpu *aarch64_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  struct kvm_vcpu_init *init, void *guest_code)
+void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
+{
+	vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc), (uint64_t)guest_code);
+}
+
+static struct kvm_vcpu *__aarch64_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
+					   struct kvm_vcpu_init *init)
 {
 	size_t stack_size;
 	uint64_t stack_vaddr;
@@ -381,15 +386,22 @@ struct kvm_vcpu *aarch64_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 	aarch64_vcpu_setup(vcpu, init);
 
 	vcpu_set_reg(vcpu, ARM64_CORE_REG(sp_el1), stack_vaddr + stack_size);
-	vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc), (uint64_t)guest_code);
+	return vcpu;
+}
+
+struct kvm_vcpu *aarch64_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
+				  struct kvm_vcpu_init *init, void *guest_code)
+{
+	struct kvm_vcpu *vcpu = __aarch64_vcpu_add(vm, vcpu_id, init);
+
+	vcpu_arch_set_entry_point(vcpu, guest_code);
 
 	return vcpu;
 }
 
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  void *guest_code)
+struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
 {
-	return aarch64_vcpu_add(vm, vcpu_id, NULL, guest_code);
+	return __aarch64_vcpu_add(vm, vcpu_id, NULL);
 }
 
 void vcpu_args_set(struct kvm_vcpu *vcpu, unsigned int num, ...)

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

@@ -277,8 +277,12 @@ static void __aligned(16) guest_unexp_trap(void)
 		  0, 0, 0, 0, 0, 0);
 }
 
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  void *guest_code)
+void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
+{
+	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.pc), (unsigned long)guest_code);
+}
+
+struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
 {
 	int r;
 	size_t stack_size;
@@ -312,7 +316,6 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 
 	/* Setup stack pointer and program counter of guest */
 	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.sp), stack_vaddr + stack_size);
-	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.pc), (unsigned long)guest_code);
 
 	/* Setup default exception vector of guest */
 	vcpu_set_reg(vcpu, RISCV_GENERAL_CSR_REG(stvec), (unsigned long)guest_unexp_trap);

tools/testing/selftests/kvm/lib/s390x/processor.c

@@ -155,15 +155,18 @@ void virt_arch_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent)
 	virt_dump_region(stream, vm, indent, vm->pgd);
 }
 
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  void *guest_code)
+void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
+{
+	vcpu->run->psw_addr = (uintptr_t)guest_code;
+}
+
+struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
 {
 	size_t stack_size =  DEFAULT_STACK_PGS * getpagesize();
 	uint64_t stack_vaddr;
 	struct kvm_regs regs;
 	struct kvm_sregs sregs;
 	struct kvm_vcpu *vcpu;
-	struct kvm_run *run;
 
 	TEST_ASSERT(vm->page_size == 4096, "Unsupported page size: 0x%x",
 		    vm->page_size);
@@ -184,9 +187,7 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 	sregs.crs[1] = vm->pgd | 0xf;		/* Primary region table */
 	vcpu_sregs_set(vcpu, &sregs);
 
-	run = vcpu->run;
-	run->psw_mask = 0x0400000180000000ULL;  /* DAT enabled + 64 bit mode */
-	run->psw_addr = (uintptr_t)guest_code;
+	vcpu->run->psw_mask = 0x0400000180000000ULL;  /* DAT enabled + 64 bit mode */
 
 	return vcpu;
 }

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

@@ -562,8 +562,16 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm)
 	sync_global_to_guest(vm, host_cpu_is_amd);
 }
 
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
-				  void *guest_code)
+void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
+{
+	struct kvm_regs regs;
+
+	vcpu_regs_get(vcpu, &regs);
+	regs.rip = (unsigned long) guest_code;
+	vcpu_regs_set(vcpu, &regs);
+}
+
+struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
 {
 	struct kvm_mp_state mp_state;
 	struct kvm_regs regs;
@@ -597,7 +605,6 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
 	vcpu_regs_get(vcpu, &regs);
 	regs.rflags = regs.rflags | 0x2;
 	regs.rsp = stack_vaddr;
-	regs.rip = (unsigned long) guest_code;
 	vcpu_regs_set(vcpu, &regs);
 
 	/* Setup the MP state */