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Subject: Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops
To: Arjan van de Ven <arjan@linux.intel.com>,
        Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>
References: <cover.1442445946.git.luto@kernel.org>
 <20150917071920.GA14296@gmail.com>
 <CALCETrUQaHKjUak6QrF9-yJxdP0_=r+uSD=gi2a6FbYuQYmj8w@mail.gmail.com>
 <55FADBE6.9040008@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, KVM list <kvm@vger.kernel.org>,
        xen-devel <Xen-devel@lists.xen.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Andrew Morton <akpm@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <55FADC3D.70202@redhat.com>
Date: Thu, 17 Sep 2015 17:29:01 +0200
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On 17/09/2015 17:27, Arjan van de Ven wrote:
>>
>>> ( We should double check that rdmsr()/wrmsr() results are never left
>>>    uninitialized, but are set to zero or so, for cases where the
>>> return code is not
>>>    checked. )
>>
>> It sure looks like native_read_msr_safe doesn't clear the output if
>> the rdmsr fails.
> 
> I'd suggest to return some poison not just 0...

What about 0 + WARN?

Paolo

> less likely to get interesting surprises that are insane hard to
> debug/diagnose