From mboxrd@z Thu Jan  1 00:00:00 1970
From: "tiejun.chen" <tiejun.chen@windriver.com>
Subject: Re: [RFC PATCH v2 1/6] kvm: add device control API
Date: Wed, 3 Apr 2013 09:28:01 +0800
Message-ID: <515B85A1.4000602@windriver.com>
References: <1360820960-12537-1-git-send-email-scottwood@freescale.com> <1364856473-25245-1-git-send-email-scottwood@freescale.com> <1364856473-25245-2-git-send-email-scottwood@freescale.com> <515A81ED.9060106@windriver.com> <1364923807.24520.2@snotra>
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Cc: Alexander Graf <agraf@suse.de>, <kvm-ppc@vger.kernel.org>,
	<kvm@vger.kernel.org>, <paulus@samba.org>
To: Scott Wood <scottwood@freescale.com>
Return-path: <kvm-ppc-owner@vger.kernel.org>
In-Reply-To: <1364923807.24520.2@snotra>
Sender: kvm-ppc-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On 04/03/2013 01:30 AM, Scott Wood wrote:
> On 04/02/2013 01:59:57 AM, tiejun.chen wrote:
>> On 04/02/2013 06:47 AM, Scott Wood wrote:
>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>> index ff71541..ed033c0 100644
>>> --- a/virt/kvm/kvm_main.c
>>> +++ b/virt/kvm/kvm_main.c
>>> @@ -2158,6 +2158,17 @@ out:
>>>   }
>>>   #endif
>>>
>>> +static int kvm_ioctl_create_device(struct kvm *kvm,
>>> +                   struct kvm_create_device *cd)
>>> +{
>>> +    bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
>>> +
>>> +    switch (cd->type) {
>>> +    default:
>>> +        return -ENODEV;
>>> +    }
>>
>> Even after apply patch 5, looks here still misses something like:
>>
>>     if (test)
>>         WARN_ON_ONCE(!cd->type);
>
> Why?  How does userspace passing in a bad type value mean the kernel needs to
> report internal badness, why is a value of zero worse than any other bad value,
> and why only when the test flag is set?

I just mean we need do something here since looks the 'test' variable is defined 
but unused, right? But please correct this as you expect :)

And if the userspace can't guarantee cd->type is never zero, we should return 
-ENODEV as well after that switch().

Tiejun