[PATCH v6 13/16] KVM: selftests: Refactor allocating guest stack into a helper

[Yosry Ahmed <yosry@kernel.org>]

In preparation for reusing the logic to allocate stacks for nested
guests, refactoring allocating a guest stack and aligning RSP into a
helper.

No functional change intended.

Signed-off-by: Yosry Ahmed <yosry@kernel.org>
---
 .../testing/selftests/kvm/lib/x86/processor.c | 45 ++++++++++---------
 1 file changed, 25 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index b51467d70f6e7..94a1cadb2b26b 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -778,6 +778,30 @@ void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
 		REPORT_GUEST_ASSERT(uc);
 }
 
+static gva_t vm_alloc_stack(struct kvm_vm *vm, int nr_pages)
+{
+	int size = nr_pages * getpagesize();
+	gva_t stack_gva;
+
+	stack_gva = __vm_alloc(vm, size, DEFAULT_GUEST_STACK_VADDR_MIN, MEM_REGION_DATA);
+	stack_gva += size;
+
+	/*
+	 * Align stack to match calling sequence requirements in section "The
+	 * Stack Frame" of the System V ABI AMD64 Architecture Processor
+	 * Supplement, which requires the value (%rsp + 8) to be a multiple of
+	 * 16 when control is transferred to the function entry point.
+	 *
+	 * If this code is ever used to launch a vCPU with 32-bit entry point it
+	 * may need to subtract 4 bytes instead of 8 bytes.
+	 */
+	TEST_ASSERT(IS_ALIGNED(stack_gva, PAGE_SIZE),
+		    "__vm_alloc() did not provide a page-aligned address");
+	stack_gva -= 8;
+
+	return stack_gva;
+}
+
 void kvm_arch_vm_post_create(struct kvm_vm *vm, unsigned int nr_vcpus)
 {
 	int r;
@@ -820,27 +844,8 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, u32 vcpu_id)
 {
 	struct kvm_mp_state mp_state;
 	struct kvm_regs regs;
-	gva_t stack_gva;
 	struct kvm_vcpu *vcpu;
 
-	stack_gva = __vm_alloc(vm, DEFAULT_STACK_PGS * getpagesize(),
-			       DEFAULT_GUEST_STACK_VADDR_MIN, MEM_REGION_DATA);
-
-	stack_gva += DEFAULT_STACK_PGS * getpagesize();
-
-	/*
-	 * Align stack to match calling sequence requirements in section "The
-	 * Stack Frame" of the System V ABI AMD64 Architecture Processor
-	 * Supplement, which requires the value (%rsp + 8) to be a multiple of
-	 * 16 when control is transferred to the function entry point.
-	 *
-	 * If this code is ever used to launch a vCPU with 32-bit entry point it
-	 * may need to subtract 4 bytes instead of 8 bytes.
-	 */
-	TEST_ASSERT(IS_ALIGNED(stack_gva, PAGE_SIZE),
-		    "__vm_alloc() did not provide a page-aligned address");
-	stack_gva -= 8;
-
 	vcpu = __vm_vcpu_add(vm, vcpu_id);
 	vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid());
 	vcpu_init_sregs(vm, vcpu);
@@ -849,7 +854,7 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, u32 vcpu_id)
 	/* Setup guest general purpose registers */
 	vcpu_regs_get(vcpu, &regs);
 	regs.rflags = regs.rflags | 0x2;
-	regs.rsp = stack_gva;
+	regs.rsp = vm_alloc_stack(vm, DEFAULT_STACK_PGS);
 	vcpu_regs_set(vcpu, &regs);
 
 	/* Setup the MP state */
-- 
2.54.0.545.g6539524ca2-goog