linux-kernel - Re: [PATCH] kvm mmu: reduce 50% memory usage

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Message-ID: <20100507201416.GA12974@amt.cnet>
Date:	Fri, 7 May 2010 17:14:16 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	kvm@...r.kernel.org
Subject: Re: [PATCH] kvm mmu: reduce 50% memory usage

On Fri, May 07, 2010 at 04:25:36PM +0800, Lai Jiangshan wrote:
> Subject: [PATCH] kvm, tdp: calculate correct base gfn for non-DIR level
> 
> the base gfn calculation is incorrect in __direct_map(),
> it does not calculate correctly when level=3 or 4.
> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> Reported-by: Marcelo Tosatti <mtosatti@...hat.com>
> ---
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index a5c6719..6986a6f 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1955,7 +1956,10 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
>  		}
>  
>  		if (*iterator.sptep == shadow_trap_nonpresent_pte) {
> -			pseudo_gfn = (iterator.addr & PT64_DIR_BASE_ADDR_MASK) >> PAGE_SHIFT;
> +			u64 base_addr = iterator.addr;
> +
> +			base_addr &= PT64_LVL_ADDR_MASK(iterator.level);
> +			pseudo_gfn = base_addr >> PAGE_SHIFT;
>  			sp = kvm_mmu_get_page(vcpu, pseudo_gfn, iterator.addr,
>  					      iterator.level - 1,
>  					      1, ACC_ALL, iterator.sptep);

Looks good, please resend the whole patch.
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