linux-kernel - Re: [PATCH] KVM: MMU: fix huge page adapted on non-PAE host

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Message-ID: <4FC35A15.6080000@redhat.com>
Date:	Mon, 28 May 2012 13:57:25 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH] KVM: MMU: fix huge page adapted on non-PAE host

On 05/28/2012 09:10 AM, Xiao Guangrong wrote:
> The huge page size is 4M on non-PAE host, but 2M page size is used in
> transparent_hugepage_adjust(), so the page we get after adjust the
> mapping level is not the head page, the BUG_ON() will be triggered
> 
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 72102e0..be3cea4 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2595,8 +2595,7 @@ static void transparent_hugepage_adjust(struct kvm_vcpu *vcpu,
>  			*gfnp = gfn;
>  			kvm_release_pfn_clean(pfn);
>  			pfn &= ~mask;
> -			if (!get_page_unless_zero(pfn_to_page(pfn)))
> -				BUG();
> +			kvm_get_pfn(pfn);
>  			*pfnp = pfn;
>  		}
>  	}

Shouldn't we adjust mask instead?

-- 
error compiling committee.c: too many arguments to function
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