linux-kernel - Re: [PATCH] KVM MMU: check reserved bits only if CR4.PSE=1 or CR4.PAE=1

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Date:	Tue, 16 Mar 2010 07:31:40 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Sheng Yang <sheng@...ux.intel.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KVM MMU: check reserved bits only if CR4.PSE=1 or CR4.PAE=1

On 03/16/2010 08:21 PM, Xiao Guangrong wrote:
> The RSV bit is possibility set in error code when #PF occurred
> only if CR4.PSE=1 or CR4.PAE=1
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@...fujitsu.com>
> ---
>   arch/x86/kvm/mmu.c |    3 +++
>   1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 741373e..36e50ab 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2270,6 +2270,9 @@ static bool is_rsvd_bits_set(struct kvm_vcpu *vcpu, u64 gpte, int level)
>   {
>   	int bit7;
>
> +	if (!is_pae(vcpu)&&  !is_pse(vcpu))
> +		return 0;
> +
>   	bit7 = (gpte>>  7)&  1;
>   	return (gpte&  vcpu->arch.mmu.rsvd_bits_mask[bit7][level-1]) != 0;
>   }
>    

Should be handled by reset_rsvd_bits_mask(), so that all reserved bit 
handling happens in one place.

I think the only change is that is !is_pse(vcpu) we ignore bit 7?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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