linux-kernel - [PATCH 2/4] RISC-V: KVM: Add support for software check exception

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Message-Id: <0f23f96ee5abc5c445f1f482130e8efa33e7b97c.1764509485.git.zhouquan@iscas.ac.cn>
Date: Mon,  1 Dec 2025 09:28:35 +0800
From: zhouquan@...as.ac.cn
To: anup@...infault.org,
	ajones@...tanamicro.com,
	atishp@...shpatra.org,
	paul.walmsley@...ive.com,
	palmer@...belt.com
Cc: linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org,
	Quan Zhou <zhouquan@...as.ac.cn>
Subject: [PATCH 2/4] RISC-V: KVM: Add support for software check exception

From: Quan Zhou <zhouquan@...as.ac.cn>

zicfiss / zicfilp introduces a new exception to priv isa `software check
exception` with cause code = 18. Delegate this exception to VS mode because
cfi violations in VU/VS will be reported via this exception.

RISC-V KVM should ensure that even if the SBI implementation ignores
hedeleg settings and routes VS-mode software check exceptions to HS mode,
KVM still correctly forwards them to the guest. Otherwise, these exceptions
would exit to userspace and terminate the guest.

Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
---
 arch/riscv/include/asm/csr.h      | 1 +
 arch/riscv/include/asm/kvm_host.h | 3 ++-
 arch/riscv/kvm/vcpu_exit.c        | 3 +++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 4a37a98398ad..9f10ef69de30 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -108,6 +108,7 @@
 #define EXC_INST_PAGE_FAULT	12
 #define EXC_LOAD_PAGE_FAULT	13
 #define EXC_STORE_PAGE_FAULT	15
+#define EXC_SOFTWARE_CHECK		18
 #define EXC_INST_GUEST_PAGE_FAULT	20
 #define EXC_LOAD_GUEST_PAGE_FAULT	21
 #define EXC_VIRTUAL_INST_FAULT		22
diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 4d794573e3db..0bb4da1c73df 100644
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -53,7 +53,8 @@
 					 BIT(EXC_SYSCALL)         | \
 					 BIT(EXC_INST_PAGE_FAULT) | \
 					 BIT(EXC_LOAD_PAGE_FAULT) | \
-					 BIT(EXC_STORE_PAGE_FAULT))
+					 BIT(EXC_STORE_PAGE_FAULT)) | \
+					 BIT(EXC_SOFTWARE_CHECK)
 
 #define KVM_HIDELEG_DEFAULT		(BIT(IRQ_VS_SOFT)  | \
 					 BIT(IRQ_VS_TIMER) | \
diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
index 0bb0c51e3c89..5ab8e87ed248 100644
--- a/arch/riscv/kvm/vcpu_exit.c
+++ b/arch/riscv/kvm/vcpu_exit.c
@@ -243,6 +243,9 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		run->exit_reason = KVM_EXIT_DEBUG;
 		ret = 0;
 		break;
+	case EXC_SOFTWARE_CHECK:
+		ret = vcpu_redirect(vcpu, trap);
+		break;
 	default:
 		break;
 	}
-- 
2.34.1