Re: [PATCH 2/3] KVM: MMU: Introduce a helper to read guest pte

[Avi Kivity <avi@redhat.com>]

On 04/18/2011 09:34 PM, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa<yoshikawa.takuya@oss.ntt.co.jp>
>
> This will be optimized later.
>
> Signed-off-by: Takuya Yoshikawa<yoshikawa.takuya@oss.ntt.co.jp>
> ---
>   arch/x86/kvm/paging_tmpl.h |   12 +++++++++---
>   1 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 74f8567..109939a 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -109,6 +109,14 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte)
>   	return access;
>   }
>
> +static int FNAME(read_guest_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> +				 gfn_t table_gfn, int offset, pt_element_t *ptep)
> +{
> +	return kvm_read_guest_page_mmu(vcpu, mmu, table_gfn, ptep,
> +				       offset, sizeof(*ptep),
> +				       PFERR_USER_MASK | PFERR_WRITE_MASK);
> +}
> +
>   /*
>    * Fetch a guest pte for a guest virtual address
>    */
> @@ -160,9 +168,7 @@ walk:
>   		walker->table_gfn[walker->level - 1] = table_gfn;
>   		walker->pte_gpa[walker->level - 1] = pte_gpa;
>
> -		if (kvm_read_guest_page_mmu(vcpu, mmu, table_gfn,&pte,
> -					    offset, sizeof(pte),
> -					    PFERR_USER_MASK|PFERR_WRITE_MASK)) {
> +		if (FNAME(read_guest_pte)(vcpu, mmu, table_gfn, offset,&pte)) {
>   			present = false;
>   			break;
>   		}


I think it's better to avoid a separate function for this.  The reason 
is I'd like to use ptep_user for cmpxchg_gpte() later on in 
walk_addr_generic(), so we use the same calculation for both read and 
write.  So please just inline the new code in walk_addr_generic().

In fact there's probably a bug there for nested npt - we use 
gfn_to_page(table_gfn), but table_gfn is actually an ngfn, not a gfn.  
Joerg, am I right here?

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