gma: Map dummy PTEs for buggy VT-d
Extend Setup_Default_GTT() to add 128 dummy page table entries
after the framebuffer. Apparently the IOMMU may report spurious
type 6 errors if nothing is mapped in this range. Also check for
correct alignment of the start of the framebuffer and that the
additonal PTEs fit into the GTT.
Without such dummy entries, an OS driver might report failed
reads at random addresses. It may or may not look like this:
DMAR: [DMA Read] Request device [00:02.0] PASID ffffffff fault addr\
5669eb8000 [fault reason 06] PTE Read access is not set
Change-Id: I1b97c6b44c1ffb37d119541c1c97ffe21d244da8
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/40499
Reviewed-by: Michael Niewöhner
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
diff --git a/common/hw-gfx-gma.adb b/common/hw-gfx-gma.adb
index be623e4..9157bbe 100644
--- a/common/hw-gfx-gma.adb
+++ b/common/hw-gfx-gma.adb
@@ -603,9 +603,10 @@
function Valid_FB (FB : Framebuffer_Type) return Boolean is
(Valid_Stride (FB) and
FB_First_Page (FB) in GTT_Range and
- FB_Last_Page (FB) in GTT_Range and
+ FB_Last_Page (FB) + 128 in GTT_Range and
(not Rotation_90 (FB) or
- (FB_Last_Page (FB) + GTT_Rotation_Offset in GTT_Range and
+ (FB_First_Page (FB) mod 64 = 0 and
+ FB_Last_Page (FB) + 128 + GTT_Rotation_Offset in GTT_Range and
FB.Offset >= Word32 (GTT_Rotation_Offset) * GTT_Page_Size)));
-- Also check that we don't overflow the GTT's 39-bit space
@@ -650,6 +651,10 @@
Valid => True);
Phys_Addr := Phys_Addr + GTT_Page_Size;
end loop;
+ -- Add another 128 dummy pages to work around buggy VT-d
+ for Idx in FB_Last_Page (FB) + 1 .. FB_Last_Page (FB) + 128 loop
+ Registers.Write_GTT (Idx, Phys_Addr, True);
+ end loop;
if Rotation_90 (FB) and FB.Tiling = Y_Tiled and FB.V_Stride >= 32 then
declare
@@ -673,6 +678,10 @@
end if;
end loop;
end;
+ -- Add another 128 dummy pages to work around buggy VT-d
+ for Idx in FB_Last_Page (FB) + 1 .. FB_Last_Page (FB) + 128 loop
+ Registers.Write_GTT (GTT_Rotation_Offset + Idx, Phys_Addr, True);
+ end loop;
end if;
end Setup_Default_GTT;
@@ -752,6 +761,9 @@
Pre => Is_Initialized,
Post => (if Valid then Valid_FB (FB))
is
+ GTT_Off : constant Natural :=
+ (if Rotation_90 (FB) then GTT_Rotation_Offset else 0);
+
GTT_Size, Aperture_Size : Natural;
Stolen_Size : Stolen_Size_Range;
begin
@@ -761,8 +773,10 @@
Decode_Stolen (GTT_Size, Stolen_Size);
Dev.Resource_Size (Aperture_Size, PCI.Res2);
Valid :=
- FB_Last_Page (FB) < GTT_Size / Config.GTT_PTE_Size and
- FB_Last_Page (FB) < Natural (Stolen_Size / GTT_Page_Size) and
+ FB_Last_Page (FB) + 128 + GTT_Off < GTT_Size / Config.GTT_PTE_Size
+ and
+ FB_Last_Page (FB) < Natural (Stolen_Size / GTT_Page_Size)
+ and
FB_Last_Page (FB) < Aperture_Size / GTT_Page_Size;
pragma Debug (not Valid, Debug.Put_Line
("Stolen memory too small to hold framebuffer."));