[RFC PATCH v3 05/31] KVM: selftests: Refactor steps in vCPU descriptor table initialization

[Ackerley Tng <ackerleytng@google.com>]

Split the vCPU descriptor table initialization process into a few
steps and expose them:

+ Setting up the IDT
+ Syncing exception handlers into the guest

In kvm_setup_idt(), we conditionally allocate guest memory for vm->idt
to avoid double allocation when kvm_setup_idt() is used after
vm_init_descriptor_tables().

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 .../selftests/kvm/include/x86_64/processor.h  |  2 ++
 .../selftests/kvm/lib/x86_64/processor.c      | 19 ++++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 74e0d3698f30c..abaaab4d885c1 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -750,6 +750,8 @@ struct ex_regs {
 	uint64_t rflags;
 };
 
+void kvm_setup_idt(struct kvm_vm *vm, struct kvm_dtable *dt);
+void sync_exception_handlers_to_guest(struct kvm_vm *vm);
 void vm_init_descriptor_tables(struct kvm_vm *vm);
 void vcpu_init_descriptor_tables(struct kvm_vcpu *vcpu);
 void vm_install_exception_handler(struct kvm_vm *vm, int vector,
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 3046b555fee49..1ea1019d48c13 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1174,19 +1174,32 @@ void vm_init_descriptor_tables(struct kvm_vm *vm)
 			DEFAULT_CODE_SELECTOR);
 }
 
+void kvm_setup_idt(struct kvm_vm *vm, struct kvm_dtable *dt)
+{
+	if (!vm->idt)
+		vm->idt = vm_vaddr_alloc_page(vm);
+
+	dt->base = vm->idt;
+	dt->limit = NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
+}
+
+void sync_exception_handlers_to_guest(struct kvm_vm *vm)
+{
+	*(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
+}
+
 void vcpu_init_descriptor_tables(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vm *vm = vcpu->vm;
 	struct kvm_sregs sregs;
 
 	vcpu_sregs_get(vcpu, &sregs);
-	sregs.idt.base = vm->idt;
-	sregs.idt.limit = NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
+	kvm_setup_idt(vcpu->vm, &sregs.idt);
 	sregs.gdt.base = vm->gdt;
 	sregs.gdt.limit = getpagesize() - 1;
 	kvm_seg_set_kernel_data_64bit(NULL, DEFAULT_DATA_SELECTOR, &sregs.gs);
 	vcpu_sregs_set(vcpu, &sregs);
-	*(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
+	sync_exception_handlers_to_guest(vm);
 }
 
 void vm_install_exception_handler(struct kvm_vm *vm, int vector,
-- 
2.39.0.246.g2a6d74b583-goog