linux-kernel - Re: [PATCH] KVM: x86: Fix page-tables reserved bits

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Message-ID: <20140416220409.GB15155@amt.cnet>
Date:	Wed, 16 Apr 2014 19:04:09 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Nadav Amit <namit@...technion.ac.il>, gleb@...nel.org,
	pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com,
	x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: x86: Fix page-tables reserved bits

On Wed, Apr 16, 2014 at 02:17:08PM -0700, H. Peter Anvin wrote:
> On 04/16/2014 12:03 PM, Marcelo Tosatti wrote:
> >> @@ -3550,9 +3550,9 @@ static void reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
> >>  		break;
> >>  	case PT64_ROOT_LEVEL:
> >>  		context->rsvd_bits_mask[0][3] = exb_bit_rsvd |
> >> -			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
> >> +			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 7);
> >>  		context->rsvd_bits_mask[0][2] = exb_bit_rsvd |
> >> -			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 8);
> >> +			rsvd_bits(maxphyaddr, 51) | rsvd_bits(7, 7);
> > 
> > Bit 7 is not reserved either, for the PDPTE (its PageSize bit).
> > 
> 
> In long mode (IA-32e), bit 7 is definitely reserved.
> 
> 	-hpa

There is a separate reserved mask for PS=1, nevermind.

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