[PATCH v4 07/11] KVM: riscv: selftests: Add exception handling support

Haibo Xu
2023-12-12T09:21:00Z

Add the infrastructure for guest exception handling in riscv selftests.
Customized handlers can be enabled by vm_install_exception_handler(vector)
or vm_install_interrupt_handler().

The code is inspired from that of x86/arm64.

Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/include/riscv/processor.h | 43 ++++++++
.../selftests/kvm/lib/riscv/handlers.S | 101 ++++++++++++++++++
.../selftests/kvm/lib/riscv/processor.c | 69 ++++++++++++
4 files changed, 214 insertions(+)
create mode 100644 tools/testing/selftests/kvm/lib/riscv/handlers.S

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index bb03e278a163..671224c4b9e0 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -63,6 +63,7 @@ LIBKVM_s390x += lib/s390x/diag318_test_handler.c
LIBKVM_s390x += lib/s390x/processor.c
LIBKVM_s390x += lib/s390x/ucall.c

+LIBKVM_riscv += lib/riscv/handlers.S
LIBKVM_riscv += lib/riscv/processor.c
LIBKVM_riscv += lib/riscv/ucall.c

diff --git a/tools/testing/selftests/kvm/include/riscv/processor.h b/tools/testing/selftests/kvm/include/riscv/processor.h
index 6f9e1e5e466d..b68b1b731a34 100644
--- a/tools/testing/selftests/kvm/include/riscv/processor.h
+++ b/tools/testing/selftests/kvm/include/riscv/processor.h
@@ -42,6 +42,49 @@ static inline uint64_t __kvm_reg_id(uint64_t type, uint64_t idx,
#define RISCV_ISA_EXT_REG(idx) __kvm_reg_id(KVM_REG_RISCV_ISA_EXT, \
idx, KVM_REG_SIZE_ULONG)

+struct ex_regs {
+ unsigned long ra;
+ unsigned long sp;
+ unsigned long gp;
+ unsigned long tp;
+ unsigned long t0;
+ unsigned long t1;
+ unsigned long t2;
+ unsigned long s0;
+ unsigned long s1;
+ unsigned long a0;
+ unsigned long a1;
+ unsigned long a2;
+ unsigned long a3;
+ unsigned long a4;
+ unsigned long a5;
+ unsigned long a6;
+ unsigned long a7;
+ unsigned long s2;
+ unsigned long s3;
+ unsigned long s4;
+ unsigned long s5;
+ unsigned long s6;
+ unsigned long s7;
+ unsigned long s8;
+ unsigned long s9;
+ unsigned long s10;
+ unsigned long s11;
+ unsigned long t3;
+ unsigned long t4;
+ unsigned long t5;
+ unsigned long t6;
+ unsigned long epc;
+ unsigned long status;
+ unsigned long cause;
+};
+
+#define NR_VECTORS 2
+#define NR_EXCEPTIONS 32
+#define EC_MASK (NR_EXCEPTIONS - 1)
+
+void vm_install_interrupt_handler(struct kvm_vm *vm, exception_handler_fn handler);
+
/* L3 index Bit[47:39] */
#define PGTBL_L3_INDEX_MASK 0x0000FF8000000000ULL
#define PGTBL_L3_INDEX_SHIFT 39
diff --git a/tools/testing/selftests/kvm/lib/riscv/handlers.S b/tools/testing/selftests/kvm/lib/riscv/handlers.S
new file mode 100644
index 000000000000..aa0abd3f35bb
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/riscv/handlers.S
@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2023 Intel Corporation
+ */
+
+#ifndef __ASSEMBLY__
+#define __ASSEMBLY__
+#endif
+
+#include <asm/csr.h>
+
+.macro save_context
+ addi sp, sp, (-8*34)
+ sd x1, 0(sp)
+ sd x2, 8(sp)
+ sd x3, 16(sp)
+ sd x4, 24(sp)
+ sd x5, 32(sp)
+ sd x6, 40(sp)
+ sd x7, 48(sp)
+ sd x8, 56(sp)
+ sd x9, 64(sp)
+ sd x10, 72(sp)
+ sd x11, 80(sp)
+ sd x12, 88(sp)
+ sd x13, 96(sp)
+ sd x14, 104(sp)
+ sd x15, 112(sp)
+ sd x16, 120(sp)
+ sd x17, 128(sp)
+ sd x18, 136(sp)
+ sd x19, 144(sp)
+ sd x20, 152(sp)
+ sd x21, 160(sp)
+ sd x22, 168(sp)
+ sd x23, 176(sp)
+ sd x24, 184(sp)
+ sd x25, 192(sp)
+ sd x26, 200(sp)
+ sd x27, 208(sp)
+ sd x28, 216(sp)
+ sd x29, 224(sp)
+ sd x30, 232(sp)
+ sd x31, 240(sp)
+ csrr s0, CSR_SEPC
+ csrr s1, CSR_SSTATUS
+ csrr s2, CSR_SCAUSE
+ sd s0, 248(sp)
+ sd s1, 256(sp)
+ sd s2, 264(sp)
+.endm
+
+.macro restore_context
+ ld s2, 264(sp)
+ ld s1, 256(sp)
+ ld s0, 248(sp)
+ csrw CSR_SCAUSE, s2
+ csrw CSR_SSTATUS, s1
+ csrw CSR_SEPC, s0
+ ld x31, 240(sp)
+ ld x30, 232(sp)
+ ld x29, 224(sp)
+ ld x28, 216(sp)
+ ld x27, 208(sp)
+ ld x26, 200(sp)
+ ld x25, 192(sp)
+ ld x24, 184(sp)
+ ld x23, 176(sp)
+ ld x22, 168(sp)
+ ld x21, 160(sp)
+ ld x20, 152(sp)
+ ld x19, 144(sp)
+ ld x18, 136(sp)
+ ld x17, 128(sp)
+ ld x16, 120(sp)
+ ld x15, 112(sp)
+ ld x14, 104(sp)
+ ld x13, 96(sp)
+ ld x12, 88(sp)
+ ld x11, 80(sp)
+ ld x10, 72(sp)
+ ld x9, 64(sp)
+ ld x8, 56(sp)
+ ld x7, 48(sp)
+ ld x6, 40(sp)
+ ld x5, 32(sp)
+ ld x4, 24(sp)
+ ld x3, 16(sp)
+ ld x2, 8(sp)
+ ld x1, 0(sp)
+ addi sp, sp, (8*34)
+.endm
+
+.balign 4
+.global exception_vectors
+exception_vectors:
+ save_context
+ move a0, sp
+ call route_exception
+ restore_context
+ sret
diff --git a/tools/testing/selftests/kvm/lib/riscv/processor.c b/tools/testing/selftests/kvm/lib/riscv/processor.c
index d146ca71e0c0..efd9ac4b0198 100644
--- a/tools/testing/selftests/kvm/lib/riscv/processor.c
+++ b/tools/testing/selftests/kvm/lib/riscv/processor.c
@@ -13,6 +13,8 @@

#define DEFAULT_RISCV_GUEST_STACK_VADDR_MIN 0xac0000

+static vm_vaddr_t exception_handlers;
+
static uint64_t page_align(struct kvm_vm *vm, uint64_t v)
{
return (v + vm->page_size) & ~(vm->page_size - 1);
@@ -364,6 +366,73 @@ void vcpu_args_set(struct kvm_vcpu *vcpu, unsigned int num, ...)
va_end(ap);
}

+void kvm_exit_unexpected_exception(int vector, int ec)
+{
+ ucall(UCALL_UNHANDLED, 2, vector, ec);
+}
+
void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
{
+ struct ucall uc;
+
+ if (get_ucall(vcpu, &uc) == UCALL_UNHANDLED) {
+ TEST_FAIL("Unexpected exception (vector:0x%lx, ec:0x%lx)",
+ uc.args[0], uc.args[1]);
+ }
+}
+
+struct handlers {
+ exception_handler_fn exception_handlers[NR_VECTORS][NR_EXCEPTIONS];
+};
+
+void route_exception(struct ex_regs *regs)
+{
+ struct handlers *handlers = (struct handlers *)exception_handlers;
+ int vector = 0, ec;
+
+ ec = regs->cause & ~CAUSE_IRQ_FLAG;
+ if (ec >= NR_EXCEPTIONS)
+ goto unexpected_exception;
+
+ /* Use the same handler for all the interrupts */
+ if (regs->cause & CAUSE_IRQ_FLAG) {
+ vector = 1;
+ ec = 0;
+ }
+
+ if (handlers && handlers->exception_handlers[vector][ec])
+ return handlers->exception_handlers[vector][ec](regs);
+
+unexpected_exception:
+ return kvm_exit_unexpected_exception(vector, ec);
+}
+
+void vcpu_init_vector_tables(struct kvm_vcpu *vcpu)
+{
+ extern char exception_vectors;
+
+ vcpu_set_reg(vcpu, RISCV_CSR_REG(stvec), (unsigned long)&exception_vectors);
+}
+
+void vm_init_vector_tables(struct kvm_vm *vm)
+{
+ vm->handlers = __vm_vaddr_alloc(vm, sizeof(struct handlers),
+ vm->page_size, MEM_REGION_DATA);
+
+ *(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
+}
+
+void vm_install_exception_handler(struct kvm_vm *vm, int vector, exception_handler_fn handler)
+{
+ struct handlers *handlers = addr_gva2hva(vm, vm->handlers);
+
+ assert(vector < NR_EXCEPTIONS);
+ handlers->exception_handlers[0][vector] = handler;
+}
+
+void vm_install_interrupt_handler(struct kvm_vm *vm, exception_handler_fn handler)
+{
+ struct handlers *handlers = addr_gva2hva(vm, vm->handlers);
+
+ handlers->exception_handlers[1][0] = handler;
}
--
2.34.1