linux-kernel - Re: [PATCH 2/4] KVM: x86: Drop unnecessary goto+label in kvm_arch

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Date:   Mon, 18 Jul 2022 13:03:41 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] KVM: x86: Drop unnecessary goto+label in
 kvm_arch_init()

On Fri, 2022-07-15 at 23:00 +0000, Sean Christopherson wrote:
> Return directly if kvm_arch_init() detects an error before doing any real
> work, jumping through a label obfuscates what's happening and carries the
> unnecessary risk of leaving 'r' uninitialized.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/x86.c | 24 ++++++++----------------
>  1 file changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 12199c40f2bc..41aa3137665c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9146,21 +9146,18 @@ int kvm_arch_init(void *opaque)
>  
>         if (kvm_x86_ops.hardware_enable) {
>                 pr_err("kvm: already loaded vendor module '%s'\n", kvm_x86_ops.name);
> -               r = -EEXIST;
> -               goto out;
> +               return -EEXIST;
>         }
>  
>         if (!ops->cpu_has_kvm_support()) {
>                 pr_err_ratelimited("kvm: no hardware support for '%s'\n",
>                                    ops->runtime_ops->name);
> -               r = -EOPNOTSUPP;
> -               goto out;
> +               return -EOPNOTSUPP;
>         }
>         if (ops->disabled_by_bios()) {
>                 pr_err_ratelimited("kvm: support for '%s' disabled by bios\n",
>                                    ops->runtime_ops->name);
> -               r = -EOPNOTSUPP;
> -               goto out;
> +               return -EOPNOTSUPP;
>         }
>  
>         /*
> @@ -9170,14 +9167,12 @@ int kvm_arch_init(void *opaque)
>          */
>         if (!boot_cpu_has(X86_FEATURE_FPU) || !boot_cpu_has(X86_FEATURE_FXSR)) {
>                 printk(KERN_ERR "kvm: inadequate fpu\n");
> -               r = -EOPNOTSUPP;
> -               goto out;
> +               return -EOPNOTSUPP;
>         }
>  
>         if (IS_ENABLED(CONFIG_PREEMPT_RT) && !boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
>                 pr_err("RT requires X86_FEATURE_CONSTANT_TSC\n");
> -               r = -EOPNOTSUPP;
> -               goto out;
> +               return -EOPNOTSUPP;
>         }
>  
>         /*
> @@ -9190,21 +9185,19 @@ int kvm_arch_init(void *opaque)
>         if (rdmsrl_safe(MSR_IA32_CR_PAT, &host_pat) ||
>             (host_pat & GENMASK(2, 0)) != 6) {
>                 pr_err("kvm: host PAT[0] is not WB\n");
> -               r = -EIO;
> -               goto out;
> +               return -EIO;
>         }
>  
> -       r = -ENOMEM;
> -
>         x86_emulator_cache = kvm_alloc_emulator_cache();
>         if (!x86_emulator_cache) {
>                 pr_err("kvm: failed to allocate cache for x86 emulator\n");
> -               goto out;
> +               return -ENOMEM;
>         }
>  
>         user_return_msrs = alloc_percpu(struct kvm_user_return_msrs);
>         if (!user_return_msrs) {
>                 printk(KERN_ERR "kvm: failed to allocate percpu kvm_user_return_msrs\n");
> +               r = -ENOMEM;
>                 goto out_free_x86_emulator_cache;
>         }
>         kvm_nr_uret_msrs = 0;
> @@ -9235,7 +9228,6 @@ int kvm_arch_init(void *opaque)
>         free_percpu(user_return_msrs);
>  out_free_x86_emulator_cache:
>         kmem_cache_destroy(x86_emulator_cache);
> -out:
>         return r;
>  }
>  


I honestly don't see much value in this change, but I don't mind it either.

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky