linux-kernel - Re: [PATCH 3/4] KVM: MMU: notrap it if gpte's reserved is set

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Date:	Sun, 14 Nov 2010 12:56:10 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/4] KVM: MMU: notrap it if gpte's reserved is set

On 11/12/2010 12:34 PM, Xiao Guangrong wrote:
> We can past the page fault to guest directly if gpte's reserved
> is set
>

How can that work? shadow_notrap_nonpresent_pte causes a fault with 
PFEC.P=PFEC.RSVD=0, while we need PFEC.P=PFEC.RSVD=1.

> Signed-off-by: Xiao Guangrong<xiaoguangrong@...fujitsu.com>
> ---
>   arch/x86/kvm/paging_tmpl.h |   10 ++++++----
>   1 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 291342d..952357a 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -760,6 +760,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
>   		pt_element_t gpte;
>   		gpa_t pte_gpa;
>   		gfn_t gfn;
> +		bool gpte_invalid;
>
>   		if (!is_shadow_present_pte(sp->spt[i]))
>   			continue;
> @@ -771,12 +772,13 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
>   			return -EINVAL;
>
>   		gfn = gpte_to_gfn(gpte);
> -		if (is_rsvd_bits_set(&vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL)
> -		      || gfn != sp->gfns[i] || !is_present_gpte(gpte)
> -		      || !(gpte&  PT_ACCESSED_MASK)) {
> +		gpte_invalid = is_present_gpte(gpte) ||
> +		   is_rsvd_bits_set(&vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL);

Shouldn't that be &&?

> +		if (gpte_invalid || gfn != sp->gfns[i] ||
> +		      !(gpte&  PT_ACCESSED_MASK)) {
>   			u64 nonpresent;
>
> -			if (is_present_gpte(gpte) || !clear_unsync)
> +			if (gpte_invalid || !clear_unsync)
>   				nonpresent = shadow_trap_nonpresent_pte;
>   			else
>   				nonpresent = shadow_notrap_nonpresent_pte;


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

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