linux-kernel - Re: [PATCH 3/3] KVM: Add proper lockdep assertion in I/O bus unregister

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Date:   Thu, 15 Apr 2021 14:58:39 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Hao Sun <sunhao.th@...il.com>
Subject: Re: [PATCH 3/3] KVM: Add proper lockdep assertion in I/O bus unregister

On Mon, Apr 12, 2021 at 3:23 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Convert a comment above kvm_io_bus_unregister_dev() into an actual
> lockdep assertion, and opportunistically add curly braces to a multi-line
> for-loop.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  virt/kvm/kvm_main.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ab1fa6f92c82..ccc2ef1dbdda 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4485,21 +4485,23 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>         return 0;
>  }
>
> -/* Caller must hold slots_lock. */
>  int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>                               struct kvm_io_device *dev)
>  {
>         int i, j;
>         struct kvm_io_bus *new_bus, *bus;
>
> +       lockdep_assert_held(&kvm->slots_lock);
> +
>         bus = kvm_get_bus(kvm, bus_idx);
>         if (!bus)
>                 return 0;
>
> -       for (i = 0; i < bus->dev_count; i++)
> +       for (i = 0; i < bus->dev_count; i++) {
>                 if (bus->range[i].dev == dev) {
>                         break;
>                 }
> +       }
Per coding-style.rst, neither the for loop nor the if-block should have braces.

"Do not unnecessarily use braces where a single statement will do."

Stylistic nits aside,

Reviewed-by: Jim Mattson <jmattson@...gle.com>