linux-kernel - Re: [PATCH 2/4] KVM: selftests: Add helper macros for ioctl()s that return file descriptors

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Date:   Fri, 4 Aug 2023 16:46:22 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Michal Luczaj <mhal@...x.co>
Subject: Re: [PATCH 2/4] KVM: selftests: Add helper macros for ioctl()s that
 return file descriptors

Hi Sean,

On Thu, Aug 03, 2023 at 05:42:24PM -0700, Sean Christopherson wrote:
> Add KVM, VM, and vCPU scoped helpers for ioctl()s that return file
> descriptors, i.e. deduplicate code for asserting success on ioctls() for
> which a positive return value, not just zero, is considered success.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

I appreciate the desire to eliminate duplicate code, but I think the
naming just muddies the waters. TBH, when I first read the diff w/o the
changelog, I thought you were describing the input fd (i.e. 'kvm_fd',
'vm_fd', 'vcpu_fd'). I don't think explicitly spelling out the condition
each time (i.e. ret >= 0) is all that difficult.

[...]

>  /*
>   * Looks up and returns the value corresponding to the capability
>   * (KVM_CAP_*) given by cap.
>   */
>  static inline int vm_check_cap(struct kvm_vm *vm, long cap)
>  {
> -	int ret =  __vm_ioctl(vm, KVM_CHECK_EXTENSION, (void *)cap);
> -
> -	TEST_ASSERT(ret >= 0, KVM_IOCTL_ERROR(KVM_CHECK_EXTENSION, ret));
> -	return ret;
> +	return vm_fd_ioctl(vm, KVM_CHECK_EXTENSION, (void *)cap);
>  }

Though the same error condition, this isn't returning an fd.

-- 
Thanks,
Oliver