From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 4/5] KVM: x86: Wrong register masking in 64-bit mode
Date: Wed, 07 May 2014 17:24:00 +0200
Message-ID: <536A5010.6040206@redhat.com>
References: <1399465972-4026-1-git-send-email-namit@cs.technion.ac.il>	<1399465972-4026-5-git-send-email-namit@cs.technion.ac.il> <jpglhudej88.fsf@nelium.bos.redhat.com>
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Cc: mtosatti@redhat.com, hpa@zytor.com, gleb@kernel.org,
	tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
To: Bandan Das <bsd@redhat.com>, Nadav Amit <namit@cs.technion.ac.il>
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Il 07/05/2014 16:50, Bandan Das ha scritto:
>> > +static void assign_masked(ulong *dest, ulong src, int bytes)
>> >  {
>> > -	*dest = (*dest & ~mask) | (src & mask);
>> > +	switch (bytes) {
>> > +	case 2:
>> > +		*dest = (u16)src | (*dest & ~0xfffful);
>> > +		break;
>> > +	case 4:
>> > +		*dest = (u32)src;
>> > +		break;
>> > +	case 8:
>> > +		*dest = src;
>> > +		break;
>> > +	default:
>> > +		BUG();
> IIRC, Paolo mentioned that a WARN() is preferable. But I see
> a lot other places where BUG() is called, maybe, he can confirm.
>

There is really no reason to crash the host for a misused API, so I do 
believe that a WARN() is preferable.

Paolo