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

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Message-ID: <534EF354.3090204@zytor.com>
Date:	Wed, 16 Apr 2014 14:17:08 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Marcelo Tosatti <mtosatti@...hat.com>,
	Nadav Amit <namit@...technion.ac.il>
CC:	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 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

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