linux-kernel - [PATCH 1/5] RISC-V: KVM: Provide UAPI for Zicbop block size

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Message-Id: <553bacc4f66e815975bb8ee0e4696397407b0a82.1750164414.git.zhouquan@iscas.ac.cn>
Date: Tue, 17 Jun 2025 21:10:22 +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 1/5] RISC-V: KVM: Provide UAPI for Zicbop block size

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

We're about to allow guests to use the Zicbop extension.
KVM userspace needs to know the cache block size in order to
properly advertise it to the guest. Provide a virtual config
register for userspace to get it with the GET_ONE_REG API, but
setting it cannot be supported, so disallow SET_ONE_REG.

Signed-off-by: Quan Zhou <zhouquan@...as.ac.cn>
---
 arch/riscv/include/uapi/asm/kvm.h |  1 +
 arch/riscv/kvm/vcpu_onereg.c      | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 5f59fd226cc5..0863ca178066 100644
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -55,6 +55,7 @@ struct kvm_riscv_config {
 	unsigned long mimpid;
 	unsigned long zicboz_block_size;
 	unsigned long satp_mode;
+	unsigned long zicbop_block_size;
 };
 
 /* CORE registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index 2e1b646f0d61..b08a22eaa7a7 100644
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -256,6 +256,11 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
 			return -ENOENT;
 		reg_val = riscv_cboz_block_size;
 		break;
+	case KVM_REG_RISCV_CONFIG_REG(zicbop_block_size):
+		if (!riscv_isa_extension_available(vcpu->arch.isa, ZICBOP))
+			return -ENOENT;
+		reg_val = riscv_cbop_block_size;
+		break;
 	case KVM_REG_RISCV_CONFIG_REG(mvendorid):
 		reg_val = vcpu->arch.mvendorid;
 		break;
@@ -347,6 +352,12 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 		if (reg_val != riscv_cboz_block_size)
 			return -EINVAL;
 		break;
+	case KVM_REG_RISCV_CONFIG_REG(zicbop_block_size):
+		if (!riscv_isa_extension_available(vcpu->arch.isa, ZICBOP))
+			return -ENOENT;
+		if (reg_val != riscv_cbop_block_size)
+			return -EINVAL;
+		break;
 	case KVM_REG_RISCV_CONFIG_REG(mvendorid):
 		if (reg_val == vcpu->arch.mvendorid)
 			break;
-- 
2.34.1