Re: [PATCH 5/9] RISC-V: KVM: Provide UAPI for Zicboz block size

From: Conor Dooley <conor@kernel.org>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: linux-riscv@lists.infradead.org, kvm-riscv@lists.infradead.org,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Anup Patel <apatel@ventanamicro.com>,
	Heiko Stuebner <heiko@sntech.de>,
	Conor Dooley <conor.dooley@microchip.com>,
	Atish Patra <atishp@rivosinc.com>,
	Jisheng Zhang <jszhang@kernel.org>
Subject: Re: [PATCH 5/9] RISC-V: KVM: Provide UAPI for Zicboz block size
Date: Sun, 30 Oct 2022 21:23:05 +0000	[thread overview]
Message-ID: <Y17rOVVrkCFqVV2Q@spud> (raw)
In-Reply-To: <20221027130247.31634-6-ajones@ventanamicro.com>

On Thu, Oct 27, 2022 at 03:02:43PM +0200, Andrew Jones wrote:
> 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.

This all looks pretty formulaic..
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

> 
> Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  arch/riscv/include/uapi/asm/kvm.h | 1 +
>  arch/riscv/kvm/vcpu.c             | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index 8985ff234c01..4bbf55cb2b70 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -49,6 +49,7 @@ struct kvm_sregs {
>  struct kvm_riscv_config {
>  	unsigned long isa;
>  	unsigned long zicbom_block_size;
> +	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 71ebbc4821f0..18a739070b51 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -270,6 +270,11 @@ 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;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -329,6 +334,8 @@ 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;
>  	default:
>  		return -EINVAL;
>  	}
> -- 
> 2.37.3
> 
> 
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