xen/arm: p2m: Limit call to mem access code use in get_page_from_gva

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

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 5ca7ffe41bfdd57168455986ffb4fc191a45d4ec..ebf74760fa7bbef4f93db2d76e44d949d787bd99 100644 (file)
--- 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;
 }