linux-kernel - [PATCH] LoongArch: KVM: Add hypercall instruction emulation support

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Message-Id: <20231227070922.1411467-1-maobibo@loongson.cn>
Date: Wed, 27 Dec 2023 15:09:22 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
	Tianrui Zhao <zhaotianrui@...ngson.cn>
Cc: WANG Xuerui <kernel@...0n.name>,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: [PATCH] LoongArch: KVM: Add hypercall instruction emulation support

On LoongArch system, hypercall instruction is supported when system
runs on VM mode. This patch adds dummy function for hypercall
instruction emulation, rather than inject EXCCODE_INE invalid
instruction exception to VM.

Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
---
 arch/loongarch/include/asm/Kbuild      |  1 -
 arch/loongarch/include/asm/kvm_para.h  | 26 ++++++++++++++++++++++++++
 arch/loongarch/include/uapi/asm/Kbuild |  2 --
 arch/loongarch/kvm/exit.c              | 10 ++++++++++
 4 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 arch/loongarch/include/asm/kvm_para.h
 delete mode 100644 arch/loongarch/include/uapi/asm/Kbuild

diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm/Kbuild
index 93783fa24f6e..22991a6f0e2b 100644
--- a/arch/loongarch/include/asm/Kbuild
+++ b/arch/loongarch/include/asm/Kbuild
@@ -23,4 +23,3 @@ generic-y += poll.h
 generic-y += param.h
 generic-y += posix_types.h
 generic-y += resource.h
-generic-y += kvm_para.h
diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
new file mode 100644
index 000000000000..9425d3b7e486
--- /dev/null
+++ b/arch/loongarch/include/asm/kvm_para.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_LOONGARCH_KVM_PARA_H
+#define _ASM_LOONGARCH_KVM_PARA_H
+
+/*
+ * LoongArch hypcall return code
+ */
+#define KVM_HC_STATUS_SUCCESS		0
+#define KVM_HC_INVALID_CODE		-1UL
+#define KVM_HC_INVALID_PARAMETER	-2UL
+
+static inline unsigned int kvm_arch_para_features(void)
+{
+	return 0;
+}
+
+static inline unsigned int kvm_arch_para_hints(void)
+{
+	return 0;
+}
+
+static inline bool kvm_check_and_clear_guest_paused(void)
+{
+	return false;
+}
+#endif /* _ASM_LOONGARCH_KVM_PARA_H */
diff --git a/arch/loongarch/include/uapi/asm/Kbuild b/arch/loongarch/include/uapi/asm/Kbuild
deleted file mode 100644
index 4aa680ca2e5f..000000000000
--- a/arch/loongarch/include/uapi/asm/Kbuild
+++ /dev/null
@@ -1,2 +0,0 @@
-# SPDX-License-Identifier: GPL-2.0
-generic-y += kvm_para.h
diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
index ce8de3fa472c..f453a3e40cab 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -659,6 +659,15 @@ static int kvm_handle_fpu_disabled(struct kvm_vcpu *vcpu)
 	return RESUME_GUEST;
 }
 
+static int kvm_handle_hypcall(struct kvm_vcpu *vcpu)
+{
+	update_pc(&vcpu->arch);
+
+	/* Treat it as noop intruction, only set return value */
+	vcpu->arch.gprs[LOONGARCH_GPR_A0] = KVM_HC_INVALID_CODE;
+	return RESUME_GUEST;
+}
+
 /*
  * LoongArch KVM callback handling for unimplemented guest exiting
  */
@@ -688,6 +697,7 @@ static exit_handle_fn kvm_fault_tables[EXCCODE_INT_START] = {
 	[EXCCODE_TLBM]			= kvm_handle_write_fault,
 	[EXCCODE_FPDIS]			= kvm_handle_fpu_disabled,
 	[EXCCODE_GSPR]			= kvm_handle_gspr,
+	[EXCCODE_HVC]			= kvm_handle_hypcall,
 };
 
 int kvm_handle_fault(struct kvm_vcpu *vcpu, int fault)
-- 
2.39.3