[PATCH v2 1/4] KVM: arm64: selftests: Add GPR save/restore functions for NV
Wei-Lin Chang
weilin.chang at arm.com
Sun Apr 12 07:22:13 PDT 2026
Adapt entry.S and hyp-entry.S from arch/arm64/kvm/hyp so that guest
hypervisors can save and restore GPRs, and provide exception handlers
to regain control after the nested guest exits. Other system register
save/restore will be added later on demand.
Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
tools/testing/selftests/kvm/Makefile.kvm | 3 +
.../selftests/kvm/include/arm64/nested.h | 45 ++++++
tools/testing/selftests/kvm/lib/arm64/entry.S | 132 ++++++++++++++++++
.../selftests/kvm/lib/arm64/hyp-entry.S | 77 ++++++++++
.../testing/selftests/kvm/lib/arm64/nested.c | 12 ++
5 files changed, 269 insertions(+)
create mode 100644 tools/testing/selftests/kvm/include/arm64/nested.h
create mode 100644 tools/testing/selftests/kvm/lib/arm64/entry.S
create mode 100644 tools/testing/selftests/kvm/lib/arm64/hyp-entry.S
create mode 100644 tools/testing/selftests/kvm/lib/arm64/nested.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 98da9fa4b8b7..3dc3e39f7025 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -30,10 +30,13 @@ LIBKVM_x86 += lib/x86/svm.c
LIBKVM_x86 += lib/x86/ucall.c
LIBKVM_x86 += lib/x86/vmx.c
+LIBKVM_arm64 += lib/arm64/entry.S
LIBKVM_arm64 += lib/arm64/gic.c
LIBKVM_arm64 += lib/arm64/gic_v3.c
LIBKVM_arm64 += lib/arm64/gic_v3_its.c
LIBKVM_arm64 += lib/arm64/handlers.S
+LIBKVM_arm64 += lib/arm64/hyp-entry.S
+LIBKVM_arm64 += lib/arm64/nested.c
LIBKVM_arm64 += lib/arm64/processor.c
LIBKVM_arm64 += lib/arm64/spinlock.c
LIBKVM_arm64 += lib/arm64/ucall.c
diff --git a/tools/testing/selftests/kvm/include/arm64/nested.h b/tools/testing/selftests/kvm/include/arm64/nested.h
new file mode 100644
index 000000000000..86d931facacb
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/arm64/nested.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * ARM64 Nested virtualization defines
+ */
+
+#ifndef SELFTEST_KVM_NESTED_H
+#define SELFTEST_KVM_NESTED_H
+
+#define ARM_EXCEPTION_IRQ 0
+#define ARM_EXCEPTION_EL1_SERROR 1
+#define ARM_EXCEPTION_TRAP 2
+#define ARM_EXCEPTION_IL 3
+#define ARM_EXCEPTION_EL2_IRQ 4
+#define ARM_EXCEPTION_EL2_SERROR 5
+#define ARM_EXCEPTION_EL2_TRAP 6
+
+#ifndef __ASSEMBLER__
+
+#include <asm/ptrace.h>
+#include "kvm_util.h"
+
+extern char hyp_vectors[];
+
+struct cpu_context {
+ struct user_pt_regs regs; /* sp = sp_el0 */
+};
+
+struct vcpu {
+ struct cpu_context context;
+};
+
+/*
+ * KVM has host_data and hyp_context, combine them because we're only doing
+ * hyp context.
+ */
+struct hyp_data {
+ struct cpu_context hyp_context;
+};
+
+u64 __guest_enter(struct vcpu *vcpu, struct cpu_context *hyp_context);
+void __hyp_exception(u64 type);
+
+#endif /* !__ASSEMBLER__ */
+
+#endif /* SELFTEST_KVM_NESTED_H */
diff --git a/tools/testing/selftests/kvm/lib/arm64/entry.S b/tools/testing/selftests/kvm/lib/arm64/entry.S
new file mode 100644
index 000000000000..33bedf5e7fb2
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/arm64/entry.S
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * adapted from arch/arm64/kvm/hyp/entry.S
+ */
+
+/*
+ * Manually define these for now
+ */
+// offsetof(struct vcpu, context)
+#define CPU_CONTEXT 0
+// offsetof(struct cpu_context, regs)
+#define CPU_USER_PT_REGS 0
+
+#define CPU_XREG_OFFSET(x) (CPU_USER_PT_REGS + 8*x)
+#define CPU_LR_OFFSET CPU_XREG_OFFSET(30)
+#define CPU_SP_EL0_OFFSET (CPU_LR_OFFSET + 8)
+
+.macro save_callee_saved_regs ctxt
+ str x18, [\ctxt, #CPU_XREG_OFFSET(18)]
+ stp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
+ stp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
+ stp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
+ stp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
+ stp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
+ stp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
+.endm
+
+.macro restore_callee_saved_regs ctxt
+ ldr x18, [\ctxt, #CPU_XREG_OFFSET(18)]
+ ldp x19, x20, [\ctxt, #CPU_XREG_OFFSET(19)]
+ ldp x21, x22, [\ctxt, #CPU_XREG_OFFSET(21)]
+ ldp x23, x24, [\ctxt, #CPU_XREG_OFFSET(23)]
+ ldp x25, x26, [\ctxt, #CPU_XREG_OFFSET(25)]
+ ldp x27, x28, [\ctxt, #CPU_XREG_OFFSET(27)]
+ ldp x29, lr, [\ctxt, #CPU_XREG_OFFSET(29)]
+.endm
+
+.macro save_sp_el0 ctxt, tmp
+ mrs \tmp, sp_el0
+ str \tmp, [\ctxt, #CPU_SP_EL0_OFFSET]
+.endm
+
+.macro restore_sp_el0 ctxt, tmp
+ ldr \tmp, [\ctxt, #CPU_SP_EL0_OFFSET]
+ msr sp_el0, \tmp
+.endm
+
+/*
+ * u64 __guest_enter(struct vcpu *vcpu, struct cpu_context *hyp_context);
+ */
+.globl __guest_enter
+__guest_enter:
+ // x0: vcpu
+ // x1: hyp context
+
+ // Store vcpu and hyp context pointer on the stack
+ stp x0, x1, [sp, #-16]!
+
+ // Store the hyp regs
+ save_callee_saved_regs x1
+
+ // Save hyp's sp_el0
+ save_sp_el0 x1, x2
+
+ // x29 = vCPU user pt regs
+ add x29, x0, #CPU_CONTEXT
+
+ // Restore the guest's sp_el0
+ restore_sp_el0 x29, x0
+
+ // Restore guest regs x0-x17
+ ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)]
+ ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)]
+ ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)]
+ ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)]
+ ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)]
+ ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)]
+ ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)]
+ ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)]
+ ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)]
+
+ // Restore guest regs x18-x29, lr
+ restore_callee_saved_regs x29
+
+ // Do not touch any register after this!
+ eret
+
+.globl __guest_exit
+__guest_exit:
+ // x0: return code
+ // x1: vcpu
+ // x2-x29,lr: vcpu regs
+ // vcpu x0-x1 on the stack
+
+ add x1, x1, #CPU_CONTEXT
+
+ // Store the guest regs x2 and x3
+ stp x2, x3, [x1, #CPU_XREG_OFFSET(2)]
+
+ // Retrieve the guest regs x0-x1 from the stack
+ ldp x2, x3, [sp], #16 // x0, x1
+
+ // Store the guest regs x0-x1 and x4-x17
+ stp x2, x3, [x1, #CPU_XREG_OFFSET(0)]
+ stp x4, x5, [x1, #CPU_XREG_OFFSET(4)]
+ stp x6, x7, [x1, #CPU_XREG_OFFSET(6)]
+ stp x8, x9, [x1, #CPU_XREG_OFFSET(8)]
+ stp x10, x11, [x1, #CPU_XREG_OFFSET(10)]
+ stp x12, x13, [x1, #CPU_XREG_OFFSET(12)]
+ stp x14, x15, [x1, #CPU_XREG_OFFSET(14)]
+ stp x16, x17, [x1, #CPU_XREG_OFFSET(16)]
+
+ // Store the guest regs x18-x29, lr
+ save_callee_saved_regs x1
+
+ // Store the guest's sp_el0
+ save_sp_el0 x1, x2
+
+ // At this point x0 and x1 on the stack is popped, so next is vCPU
+ // pointer, then hyp_context pointer
+ // *sp == vCPU, *(sp + 8) == hyp_context
+ // load x2 = hyp_context, x3 is just for ldp and popping sp
+ ldp x3, x2, [sp], #16
+
+ // Restore hyp's sp_el0
+ restore_sp_el0 x2, x3
+
+ // Now restore the hyp regs
+ restore_callee_saved_regs x2
+
+ dsb sy // Synchronize against in-flight ld/st
+ ret
diff --git a/tools/testing/selftests/kvm/lib/arm64/hyp-entry.S b/tools/testing/selftests/kvm/lib/arm64/hyp-entry.S
new file mode 100644
index 000000000000..6341f6e05c90
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/arm64/hyp-entry.S
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * adapted from arch/arm64/kvm/hyp/hyp-entry.S
+ */
+
+#include "nested.h"
+
+// skip over x0, x1 saved on entry, must be used only before the stack is modified
+.macro get_vcpu_ptr vcpu
+ ldr \vcpu, [sp, #16]
+.endm
+
+ .text
+
+el1_sync: // Guest trapped into EL2
+
+ get_vcpu_ptr x1
+ mov x0, #ARM_EXCEPTION_TRAP
+ b __guest_exit
+
+el1_irq:
+el1_fiq:
+ get_vcpu_ptr x1
+ mov x0, #ARM_EXCEPTION_IRQ
+ b __guest_exit
+
+el1_error:
+ get_vcpu_ptr x1
+ mov x0, #ARM_EXCEPTION_EL1_SERROR
+ b __guest_exit
+
+el2_sync:
+ mov x0, #ARM_EXCEPTION_EL2_TRAP
+ b __hyp_exception
+
+el2_irq:
+el2_fiq:
+ mov x0, #ARM_EXCEPTION_EL2_IRQ
+ b __hyp_exception
+
+el2_error:
+ mov x0, #ARM_EXCEPTION_EL2_SERROR
+ b __hyp_exception
+
+
+ .ltorg
+
+ .align 11
+
+.globl hyp_vectors
+hyp_vectors:
+
+.macro exception_vector target
+ .align 7
+ stp x0, x1, [sp, #-16]!
+ b \target
+.endm
+
+ exception_vector el2_sync // Synchronous EL2t
+ exception_vector el2_irq // IRQ EL2t
+ exception_vector el2_fiq // FIQ EL2t
+ exception_vector el2_error // Error EL2t
+
+ exception_vector el2_sync // Synchronous EL2h
+ exception_vector el2_irq // IRQ EL2h
+ exception_vector el2_fiq // FIQ EL2h
+ exception_vector el2_error // Error EL2h
+
+ exception_vector el1_sync // Synchronous 64-bit EL1
+ exception_vector el1_irq // IRQ 64-bit EL1
+ exception_vector el1_fiq // FIQ 64-bit EL1
+ exception_vector el1_error // Error 64-bit EL1
+
+ exception_vector el1_sync // Synchronous 32-bit EL1
+ exception_vector el1_irq // IRQ 32-bit EL1
+ exception_vector el1_fiq // FIQ 32-bit EL1
+ exception_vector el1_error // Error 32-bit EL1
diff --git a/tools/testing/selftests/kvm/lib/arm64/nested.c b/tools/testing/selftests/kvm/lib/arm64/nested.c
new file mode 100644
index 000000000000..06ddaab2436f
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/arm64/nested.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ARM64 Nested virtualization helpers
+ */
+
+#include "nested.h"
+#include "test_util.h"
+
+void __hyp_exception(u64 type)
+{
+ GUEST_FAIL("Unexpected hyp exception! type: %lx\n", type);
+}
--
2.43.0
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