diff mbox series

[v6,09/15] efi: use new page table APIs in copy_mapping

Message ID 6c27c79964eb16eba4743515689b9fd7eb3409d1.1587735799.git.hongyxia@amazon.com (mailing list archive)
State Superseded
Headers show
Series switch to domheap for Xen page tables | expand

Commit Message

Hongyan Xia April 24, 2020, 2:09 p.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

After inspection ARM doesn't have alloc_xen_pagetable so this function
is x86 only, which means it is safe for us to change.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 xen/common/efi/boot.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Comments

Jan Beulich April 30, 2020, 12:42 p.m. UTC | #1 
On 24.04.2020 16:09, Hongyan Xia wrote:
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -1454,16 +1454,20 @@ static __init void copy_mapping(unsigned long mfn, unsigned long end,
>              continue;
>          if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
>          {
> -            l3dst = alloc_xen_pagetable();
> -            BUG_ON(!l3dst);
> +            mfn_t l3mfn = alloc_xen_pagetable_new();
> +
> +            BUG_ON(mfn_eq(l3mfn, INVALID_MFN));
> +            l3dst = map_domain_page(l3mfn);
>              clear_page(l3dst);
>              efi_l4_pgtable[l4_table_offset(mfn << PAGE_SHIFT)] =
> -                l4e_from_paddr(virt_to_maddr(l3dst), __PAGE_HYPERVISOR);
> +                l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR);
>          }
>          else
> -            l3dst = l4e_to_l3e(l4e);
> -        l3src = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]);
> +            l3dst = map_l3t_from_l4e(l4e);
> +        l3src = map_l3t_from_l4e(idle_pg_table[l4_table_offset(va)]);
>          l3dst[l3_table_offset(mfn << PAGE_SHIFT)] = l3src[l3_table_offset(va)];
> +        unmap_domain_page(l3src);
> +        unmap_domain_page(l3dst);
>      }
>  }

This looks very inefficient - you establish and tear down two mappings
per loop iteration, when really you may end up copying all 512 slots
between the same pair of L3 tables.

Jan
diff mbox series

Patch

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index a6f84c945a..8e96ef8de2 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1454,16 +1454,20 @@  static __init void copy_mapping(unsigned long mfn, unsigned long end,
             continue;
         if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
         {
-            l3dst = alloc_xen_pagetable();
-            BUG_ON(!l3dst);
+            mfn_t l3mfn = alloc_xen_pagetable_new();
+
+            BUG_ON(mfn_eq(l3mfn, INVALID_MFN));
+            l3dst = map_domain_page(l3mfn);
             clear_page(l3dst);
             efi_l4_pgtable[l4_table_offset(mfn << PAGE_SHIFT)] =
-                l4e_from_paddr(virt_to_maddr(l3dst), __PAGE_HYPERVISOR);
+                l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR);
         }
         else
-            l3dst = l4e_to_l3e(l4e);
-        l3src = l4e_to_l3e(idle_pg_table[l4_table_offset(va)]);
+            l3dst = map_l3t_from_l4e(l4e);
+        l3src = map_l3t_from_l4e(idle_pg_table[l4_table_offset(va)]);
         l3dst[l3_table_offset(mfn << PAGE_SHIFT)] = l3src[l3_table_offset(va)];
+        unmap_domain_page(l3src);
+        unmap_domain_page(l3dst);
     }
 }