[Xen-devel,05/15] xen/arm: p2m: Limit call to mem access code use in get_page_from_gva

Message ID 20180716172712.20294-6-julien.grall@arm.com
State New
Headers show
Series
  • xen/arm: Bunch of clean-up/improvement
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Commit Message

Julien Grall July 16, 2018, 5:27 p.m.
Mem access has only an impact on the hardware translation between a
guest virtual address and the machine physical address. So it is not
necessary to fallback to memaccess for all the other case (e.g when it
is not possible to acquire the page behind the MFN).

Signed-off-by: Julien Grall <julien.grall@arm.com>

---

Cc: Razvan Cojocaru <rcojocaru@bitdefender.com>
Cc: Tamas K Lengyel <tamas@tklengyel.com>
---
 xen/arch/arm/p2m.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

Comments

Razvan Cojocaru July 17, 2018, 9:54 a.m. | #1
On 07/16/2018 08:27 PM, Julien Grall wrote:
> Mem access has only an impact on the hardware translation between a
> guest virtual address and the machine physical address. So it is not
> necessary to fallback to memaccess for all the other case (e.g when it
> is not possible to acquire the page behind the MFN).
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>

Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>


Thanks,
Razvan
Stefano Stabellini Aug. 14, 2018, 8:59 p.m. | #2
On Mon, 16 Jul 2018, Julien Grall wrote:
> Mem access has only an impact on the hardware translation between a
> guest virtual address and the machine physical address. So it is not
> necessary to fallback to memaccess for all the other case (e.g when it
> is not possible to acquire the page behind the MFN).
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
> 
> Cc: Razvan Cojocaru <rcojocaru@bitdefender.com>
> Cc: Tamas K Lengyel <tamas@tklengyel.com>
> ---
>  xen/arch/arm/p2m.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 5ca7ffe41b..ebf74760fa 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -1425,17 +1425,24 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va,
>  
>      if ( par )
>      {
> +        /*
> +         * When memaccess is enabled, the translation GVA to MADDR may
> +         * have failed because of a permission fault.
> +         */
> +        if ( p2m->mem_access_enabled )
> +            return p2m_mem_access_check_and_get_page(va, flags, v);
> +
>          dprintk(XENLOG_G_DEBUG,
>                  "%pv: gvirt_to_maddr failed va=%#"PRIvaddr" flags=0x%lx par=%#"PRIx64"\n",
>                  v, va, flags, par);
> -        goto err;
> +        return NULL;
>      }
>  
>      if ( !mfn_valid(maddr_to_mfn(maddr)) )
>      {
>          dprintk(XENLOG_G_DEBUG, "%pv: Invalid MFN %#"PRI_mfn"\n",
>                  v, mfn_x(maddr_to_mfn(maddr)));
> -        goto err;
> +        return NULL;
>      }
>  
>      page = mfn_to_page(maddr_to_mfn(maddr));
> @@ -1445,13 +1452,9 @@ struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va,
>      {
>          dprintk(XENLOG_G_DEBUG, "%pv: Failing to acquire the MFN %#"PRI_mfn"\n",
>                  v, mfn_x(maddr_to_mfn(maddr)));
> -        page = NULL;
> +        return NULL;
>      }
>  
> -err:
> -    if ( !page && p2m->mem_access_enabled )
> -        page = p2m_mem_access_check_and_get_page(va, flags, v);
> -
>      return page;
>  }
>  
> -- 
> 2.11.0
>

Patch

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 5ca7ffe41b..ebf74760fa 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1425,17 +1425,24 @@  struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va,
 
     if ( par )
     {
+        /*
+         * When memaccess is enabled, the translation GVA to MADDR may
+         * have failed because of a permission fault.
+         */
+        if ( p2m->mem_access_enabled )
+            return p2m_mem_access_check_and_get_page(va, flags, v);
+
         dprintk(XENLOG_G_DEBUG,
                 "%pv: gvirt_to_maddr failed va=%#"PRIvaddr" flags=0x%lx par=%#"PRIx64"\n",
                 v, va, flags, par);
-        goto err;
+        return NULL;
     }
 
     if ( !mfn_valid(maddr_to_mfn(maddr)) )
     {
         dprintk(XENLOG_G_DEBUG, "%pv: Invalid MFN %#"PRI_mfn"\n",
                 v, mfn_x(maddr_to_mfn(maddr)));
-        goto err;
+        return NULL;
     }
 
     page = mfn_to_page(maddr_to_mfn(maddr));
@@ -1445,13 +1452,9 @@  struct page_info *get_page_from_gva(struct vcpu *v, vaddr_t va,
     {
         dprintk(XENLOG_G_DEBUG, "%pv: Failing to acquire the MFN %#"PRI_mfn"\n",
                 v, mfn_x(maddr_to_mfn(maddr)));
-        page = NULL;
+        return NULL;
     }
 
-err:
-    if ( !page && p2m->mem_access_enabled )
-        page = p2m_mem_access_check_and_get_page(va, flags, v);
-
     return page;
 }