linux-kernel - Re: [PATCH] KVM: x86: fix bogus warning about reserved bits

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Message-ID: <5602A01D.1020006@redhat.com>
Date:	Wed, 23 Sep 2015 14:50:37 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: fix bogus warning about reserved bits



On 23/09/2015 13:07, Borislav Petkov wrote:
>> > +	static bool first;
>> >  
>> >  	best = kvm_find_cpuid_entry(vcpu, 0, 0);
>> > +	if (first && best) {
>> > +		printk("cpuid(0).ebx = %x\n", best->ebx);
>> > +		first = false;
>> > +	} else if (first)
>> > +		printk_ratelimited("cpuid(0) not initialized yet\n");
>> > +
>> >  	return best && best->ebx == X86EMUL_CPUID_VENDOR_AuthenticAMD_ebx;
> Do I see it correctly that that "first" thing is never true?
> 
> In any case, I changed it to initialize to true but still no output from
> that function.
> 
> [  102.448438] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 4, 0xf0000000000f8)
> [  102.458706] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 3, 0xf000000000078)
> [  102.468955] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 2, 0xf000000000078)

Yeah, but I didn't totally need the output so I didn't bother answering
with yet another v2.  I'm a bit stymied and will try to find an AMD
machine inside RH (it's always a pain to install latest-and-greatest
kernel on unknown machines).  It's probably also time to buy one too...

Paolo
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