linux-kernel - Re: [PATCH v3 2/5] KVM: MMU: check guest CR3 reserved bits based on its physical address width.

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Message-ID: <b4af9303-57bb-76cd-297f-ccb9128daf29@linux.intel.com>
Date:   Thu, 24 Aug 2017 23:23:05 +0800
From:   Yu Zhang <yu.c.zhang@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        xiaoguangrong@...cent.com, joro@...tes.org
Subject: Re: [PATCH v3 2/5] KVM: MMU: check guest CR3 reserved bits based on
 its physical address width.



On 8/24/2017 9:40 PM, Paolo Bonzini wrote:
> On 24/08/2017 14:27, Yu Zhang wrote:
>> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
>> index 3ed6192..67e7ec2 100644
>> --- a/arch/x86/kvm/mmu.h
>> +++ b/arch/x86/kvm/mmu.h
>> @@ -48,6 +48,9 @@
>>   
>>   static inline u64 rsvd_bits(int s, int e)
>>   {
>> +	if (e < s)
>> +		return 0;
>> +
>>   	return ((1ULL << (e - s + 1)) - 1) << s;
>>   }
> e = s - 1 is already supported; why do you need e <= s - 2?

Sorry? I do not quite understand. When will e = s - 1?

Thanks
Yu
> Paolo
>