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: <0bce2df3-79ac-599b-19fa-8ebeaff23623@redhat.com>
Date:   Thu, 24 Aug 2017 15:40:04 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.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 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?

Paolo