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

We're about to allow guests to use the Zicboz 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: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20230224162631.405473-8-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 92af6f3f057cf7d33031343ee09e01588b7aef17..c1a1bb0fa91cb52a8b0695fa939be46eef638cd6 100644 (file)
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -52,6 +52,7 @@ struct kvm_riscv_config {
        unsigned long mvendorid;
        unsigned long marchid;
        unsigned long mimpid;
+       unsigned long zicboz_block_size;
 };
 
 /* CORE registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 7d010b0be54e1364a714c2b712b64c067c947c11..525d785ccba205512f95290a91d248e0e5d35b15 100644 (file)
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -283,6 +283,11 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
                        return -EINVAL;
                reg_val = riscv_cbom_block_size;
                break;
+       case KVM_REG_RISCV_CONFIG_REG(zicboz_block_size):
+               if (!riscv_isa_extension_available(vcpu->arch.isa, ZICBOZ))
+                       return -EINVAL;
+               reg_val = riscv_cboz_block_size;
+               break;
        case KVM_REG_RISCV_CONFIG_REG(mvendorid):
                reg_val = vcpu->arch.mvendorid;
                break;
@@ -354,6 +359,8 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
                break;
        case KVM_REG_RISCV_CONFIG_REG(zicbom_block_size):
                return -EOPNOTSUPP;
+       case KVM_REG_RISCV_CONFIG_REG(zicboz_block_size):
+               return -EOPNOTSUPP;
        case KVM_REG_RISCV_CONFIG_REG(mvendorid):
                if (!vcpu->arch.ran_atleast_once)
                        vcpu->arch.mvendorid = reg_val;