Re: [PATCH 2/2] Nested EPT: fixing issue of translate L2 gva to L1 gfn

["Egger, Christoph" <chegger@amazon.de>]

On 12.02.14 03:08, Yang Zhang wrote:
> From: Yang Zhang <yang.z.zhang@Intel.com>
> 
> There is no way to translate L2 gva to L1 gfn directly.

Why?

> To do it, we need to get L2's gfn first. Then look up the virtual EPT to get L1's gfn.
> 
> Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
> ---
>  xen/arch/x86/mm/p2m.c |   25 ++++++++++++++++++++-----
>  1 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 8f380ed..e92cfbe 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -1605,22 +1605,37 @@ unsigned long paging_gva_to_gfn(struct vcpu *v,
>          && paging_mode_hap(v->domain) 
>          && nestedhvm_is_n2(v) )
>      {
> -        unsigned long gfn;
> +        unsigned long gfn, l1gfn, exit_qual;
>          struct p2m_domain *p2m;
>          const struct paging_mode *mode;
> -        uint32_t pfec_21 = *pfec;
>          uint64_t np2m_base = nhvm_vcpu_p2m_base(v);
> +        unsigned int page_order, exit_reason;
> +        int rc;
> +        uint8_t p2m_acc;
> +        struct nestedvmx *nvmx = &vcpu_2_nvmx(v);
>  
>          /* translate l2 guest va into l2 guest gfn */
>          p2m = p2m_get_nestedp2m(v, np2m_base);
>          mode = paging_get_nestedmode(v);
>          gfn = mode->gva_to_gfn(v, p2m, va, pfec);
>  
> +        if ( gfn == INVALID_GFN )
> +            return gfn;
> +
>          /* translate l2 guest gfn into l1 guest gfn */
> -        return hostmode->p2m_ga_to_gfn(v, hostp2m, np2m_base,
> -                                       gfn << PAGE_SHIFT, &pfec_21, NULL);
> -    }

I think in p2m-ept.c you should override that function pointer to a EPT
specific implementation.

Christoph

> +        rc = nept_translate_l2ga(v, gfn << 12 , &page_order, 4, &l1gfn, &p2m_acc,
> +                                &exit_qual, &exit_reason);
> +        if ( rc == EPT_TRANSLATE_VIOLATION || rc == EPT_TRANSLATE_MISCONFIG )
> +        {
> +            nvmx->ept.exit_reason = exit_reason;
> +            nvmx->ept.exit_qual = exit_qual;
> +            vcpu_nestedhvm(current).nv_vmexit_pending = 1;
> +        }
> +        if ( rc == EPT_TRANSLATE_RETRY )
> +            *pfec = PFEC_page_paged;
>  
> +        return l1gfn;
> +    }
>      return hostmode->gva_to_gfn(v, hostp2m, va, pfec);
>  }
>  
>