From: maobibo <maobibo@loongson.cn>
To: WANG Xuerui <kernel@xen0n.name>,
Paolo Bonzini <pbonzini@redhat.com>,
Huacai Chen <chenhuacai@kernel.org>
Cc: Tianrui Zhao <zhaotianrui@loongson.cn>,
kvm@vger.kernel.org, loongarch@lists.linux.dev,
linux-kernel@vger.kernel.org, WANG Xuerui <git@xen0n.name>
Subject: Re: [PATCH for-6.8 v4 3/3] LoongArch: KVM: Streamline kvm_check_cpucfg and improve comments
Date: Thu, 22 Feb 2024 20:11:20 +0800 [thread overview]
Message-ID: <719c1a92-6ddc-f73a-0609-aa5d40dbee8a@loongson.cn> (raw)
In-Reply-To: <20240222105109.2042732-4-kernel@xen0n.name>
On 2024/2/22 下午6:51, WANG Xuerui wrote:
> From: WANG Xuerui <git@xen0n.name>
>
> All the checks currently done in kvm_check_cpucfg can be realized with
> early returns, so just do that to avoid extra cognitive burden related
> to the return value handling.
>
> While at it, clean up comments of _kvm_get_cpucfg_mask and
> kvm_check_cpucfg, by removing comments that are merely restatement of
> the code nearby, and paraphrasing the rest so they read more natural
> for English speakers (that likely are not familiar with the actual
> Chinese-influenced grammar).
>
> No functional changes intended.
>
> Signed-off-by: WANG Xuerui <git@xen0n.name>
> ---
> arch/loongarch/kvm/vcpu.c | 42 +++++++++++++++++++--------------------
> 1 file changed, 20 insertions(+), 22 deletions(-)
>
> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> index 9f63bbaf19c1..128b89d00ced 100644
> --- a/arch/loongarch/kvm/vcpu.c
> +++ b/arch/loongarch/kvm/vcpu.c
> @@ -305,20 +305,16 @@ static int _kvm_get_cpucfg_mask(int id, u64 *v)
>
> switch (id) {
> case 2:
> - /* Return CPUCFG2 features which have been supported by KVM */
> + /* CPUCFG2 features unconditionally supported by KVM */
> *v = CPUCFG2_FP | CPUCFG2_FPSP | CPUCFG2_FPDP |
> CPUCFG2_FPVERS | CPUCFG2_LLFTP | CPUCFG2_LLFTPREV |
> CPUCFG2_LAM;
> /*
> - * If LSX is supported by CPU, it is also supported by KVM,
> - * as we implement it.
> + * For the ISA extensions listed below, if one is supported
> + * by the host, then it is also supported by KVM.
> */
> if (cpu_has_lsx)
> *v |= CPUCFG2_LSX;
> - /*
> - * if LASX is supported by CPU, it is also supported by KVM,
> - * as we implement it.
> - */
> if (cpu_has_lasx)
> *v |= CPUCFG2_LASX;
>
> @@ -349,24 +345,26 @@ static int kvm_check_cpucfg(int id, u64 val)
>
> switch (id) {
> case 2:
> - /* CPUCFG2 features checking */
> if (!(val & CPUCFG2_LLFTP))
> - /* The LLFTP must be set, as guest must has a constant timer */
> - ret = -EINVAL;
> - else if ((val & CPUCFG2_FP) && (!(val & CPUCFG2_FPSP) || !(val & CPUCFG2_FPDP)))
> - /* Single and double float point must both be set when enable FP */
> - ret = -EINVAL;
> - else if ((val & CPUCFG2_LSX) && !(val & CPUCFG2_FP))
> - /* FP should be set when enable LSX */
> - ret = -EINVAL;
> - else if ((val & CPUCFG2_LASX) && !(val & CPUCFG2_LSX))
> - /* LSX, FP should be set when enable LASX, and FP has been checked before. */
> - ret = -EINVAL;
> - break;
> + /* Guests must have a constant timer */
> + return -EINVAL;
> + if ((val & CPUCFG2_FP) && (!(val & CPUCFG2_FPSP) || !(val & CPUCFG2_FPDP)))
> + /* Single and double float point must both be set when FP is enabled */
> + return -EINVAL;
> + if ((val & CPUCFG2_LSX) && !(val & CPUCFG2_FP))
> + /* LSX architecturally implies FP but val does not satisfy that */
> + return -EINVAL;
> + if ((val & CPUCFG2_LASX) && !(val & CPUCFG2_LSX))
> + /* LASX architecturally implies LSX and FP but val does not satisfy that */
> + return -EINVAL;
> + return 0;
> default:
> - break;
> + /*
> + * Values for the other CPUCFG IDs are not being further validated
> + * besides the mask check above.
> + */
> + return 0;
> }
> - return ret;
> }
>
> static int kvm_get_one_reg(struct kvm_vcpu *vcpu,
>
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
prev parent reply other threads:[~2024-02-22 12:11 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-22 10:51 [PATCH for-6.8 v4 0/3] KVM: LoongArch: Fix wrong CPUCFG ID handling WANG Xuerui
2024-02-22 10:51 ` [PATCH for-6.8 v4 1/3] LoongArch: KVM: Fix input validation of _kvm_get_cpucfg and kvm_check_cpucfg WANG Xuerui
2024-02-22 11:57 ` maobibo
2024-02-22 10:51 ` [PATCH for-6.8 v4 2/3] LoongArch: KVM: Rename _kvm_get_cpucfg to _kvm_get_cpucfg_mask WANG Xuerui
2024-02-22 11:59 ` maobibo
2024-02-22 10:51 ` [PATCH for-6.8 v4 3/3] LoongArch: KVM: Streamline kvm_check_cpucfg and improve comments WANG Xuerui
2024-02-22 12:11 ` maobibo [this message]
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