RISC-V: KVM: Provide UAPI for Zicbop block size

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@iscas.ac.cn>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/befd8403cd76d7adb97231ac993eaeb86bf2582c.1754646071.git.zhouquan@iscas.ac.cn
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: zcxGGmu

arch/riscv/include/uapi/asm/kvm.h

@@ -56,6 +56,7 @@ 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 */

arch/riscv/kvm/vcpu_onereg.c

@@ -285,6 +285,11 @@ 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(NULL, ZICBOP))
+			return -ENOENT;
+		reg_val = riscv_cbop_block_size;
+		break;
 	case KVM_REG_RISCV_CONFIG_REG(mvendorid):
 		reg_val = vcpu->arch.mvendorid;
 		break;
@@ -376,6 +381,12 @@ 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(NULL, 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;
@@ -821,6 +832,9 @@ static int copy_config_reg_indices(const struct kvm_vcpu *vcpu,
 		else if (i == KVM_REG_RISCV_CONFIG_REG(zicboz_block_size) &&
 			!riscv_isa_extension_available(NULL, ZICBOZ))
 			continue;
+		else if (i == KVM_REG_RISCV_CONFIG_REG(zicbop_block_size) &&
+			!riscv_isa_extension_available(NULL, ZICBOP))
+			continue;
 
 		size = IS_ENABLED(CONFIG_32BIT) ? KVM_REG_SIZE_U32 : KVM_REG_SIZE_U64;
 		reg = KVM_REG_RISCV | size | KVM_REG_RISCV_CONFIG | i;