linux-kernel - RE: [PATCH V5 2/8] x86/hyperv: Set Virtual Trust Level in VMBus init message

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Date:   Fri, 11 Aug 2023 22:16:19 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Wei Liu <wei.liu@...nel.org>
CC:     Tianyu Lan <ltykernel@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>
Subject: RE: [PATCH V5 2/8] x86/hyperv: Set Virtual Trust Level in VMBus init
 message

> From: Wei Liu <wei.liu@...nel.org>
> Sent: Friday, August 11, 2023 2:15 PM
> To: Dexuan Cui <decui@...rosoft.com>
> > [...]
> > > +	local_irq_save(flags);
> > > +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> > > +	output = (struct hv_get_vp_registers_output *)input;
> > > +	if (!input) {
> > > +		local_irq_restore(flags);
> > > +		goto done;
> >
> > Here the uninitialized 'ret' is returned.
> >
> > If we move the "done:" label one line earlier, we won't need the
> > the above " local_irq_restore(flags);"
> > Maybe we should add a WARN_ON_ONCE(1) before "goto done"?
> 
> Out of interest why will input be NULL here?
> 
> Thanks,
> Wei.

I don't think 'input' could be NULL here.
IMO we can use it without checking against NULL.