[PATCH v15 14/23] KVM: selftests: Expose function to allocate vCPU stack

[Lisa Wang]

From: Sagi Shahar <sagis@xxxxxxxxxx>

Introduce kvm_allocate_vcpu_stack() to allocate a vCPU's stack
in preparation for TDX to allocate a vCPU's stack and initialize
its stack pointer.

TDX VMs' registers are protected state and cannot be initialized
using the KVM_SET_REGS ioctl() that is used for normal VMs. A TDX
vCPU's stack address will be a property of the TDX specific boot code
that initializes the vCPUs' stack pointers at boot.

Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
Signed-off-by: Lisa Wang <wyihan@xxxxxxxxxx>
Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
 .../testing/selftests/kvm/include/x86/processor.h  |  2 ++
 tools/testing/selftests/kvm/lib/x86/processor.c    | 25 +++++++++++++++++++---
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 8854ee052d29..1eb380dd216c 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -1212,6 +1212,8 @@ static inline void vcpu_clear_cpuid_feature(struct kvm_vcpu *vcpu,
 	vcpu_set_or_clear_cpuid_feature(vcpu, feature, false);
 }
 
+gva_t kvm_allocate_vcpu_stack(struct kvm_vm *vm);
+
 u64 vcpu_get_msr(struct kvm_vcpu *vcpu, u64 msr_index);
 int _vcpu_set_msr(struct kvm_vcpu *vcpu, u64 msr_index, u64 msr_value);
 
diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index da430d4e7765..4a753fb43007 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -851,12 +851,31 @@ void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
 	vcpu_regs_set(vcpu, &regs);
 }
 
-struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, u32 vcpu_id)
+gva_t kvm_allocate_vcpu_stack(struct kvm_vm *vm)
 {
 	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);
@@ -864,8 +883,8 @@ 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 | X86_EFLAGS_FIXED;
-	regs.rsp = vm_alloc_stack(vm, DEFAULT_STACK_PGS);
+	regs.rflags = regs.rflags | 0x2;
+	regs.rsp = kvm_allocate_vcpu_stack(vm);
 	vcpu_regs_set(vcpu, &regs);
 
 	/* Setup the MP state */

-- 
2.56.0.rc1.315.gc6ed9934b7-goog