Re: [PATCH v4 2/6] LoongArch: KVM: Add hypercall instruction emulation support

From: maobibo
Date: Sun Feb 18 2024 - 23:01:25 EST



On 2024/2/19 上午10:41, Huacai Chen wrote:
Hi, Bibo,

On Thu, Feb 1, 2024 at 11:19 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:

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

Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
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
Maybe using "hypercall" in comments is better.
will modify in next patch.


+ */
+#define KVM_HC_STATUS_SUCCESS 0
+#define KVM_HC_INVALID_CODE -1UL
+#define KVM_HC_INVALID_PARAMETER -2UL
Maybe KVM_HCALL_SUCCESS/KVM_HCALL_INVALID_CODE/KVM_HCALL_PARAMETER is better.
yes, KVM_HCALL_xxxx sounds better. Will modify it.

Regards
Bibo Mao

Huacai

+
+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 ed1d89d53e2e..d15c71320a11 100644
--- a/arch/loongarch/kvm/exit.c
+++ b/arch/loongarch/kvm/exit.c
@@ -685,6 +685,15 @@ static int kvm_handle_lasx_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
*/
@@ -716,6 +725,7 @@ static exit_handle_fn kvm_fault_tables[EXCCODE_INT_START] = {
[EXCCODE_LSXDIS] = kvm_handle_lsx_disabled,
[EXCCODE_LASXDIS] = kvm_handle_lasx_disabled,
[EXCCODE_GSPR] = kvm_handle_gspr,
+ [EXCCODE_HVC] = kvm_handle_hypcall,
};

int kvm_handle_fault(struct kvm_vcpu *vcpu, int fault)
--
2.39.3