[PATCH] xen/x86: obtain upper 32 bits of video frame buffer address for Dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

The hypervisor has been supplying this information for a couple of major
releases. Make use of it. The need to set a flag in the capabilities
field also points out that the prior setting of that field from the
hypervisor interface's gbl_caps one was wrong, so that code gets deleted
(there's also no equivalent of this in native boot code).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/arch/x86/xen/vga.c
+++ b/arch/x86/xen/vga.c
@@ -63,13 +63,17 @@ void __init xen_init_vga(const struct do
                }
 
                if (size >= offsetof(struct dom0_vga_console_info,
-                                    u.vesa_lfb.gbl_caps)
-                   + sizeof(info->u.vesa_lfb.gbl_caps))
-                       screen_info->capabilities = info->u.vesa_lfb.gbl_caps;
-               if (size >= offsetof(struct dom0_vga_console_info,
                                     u.vesa_lfb.mode_attrs)
                    + sizeof(info->u.vesa_lfb.mode_attrs))
                        screen_info->vesa_attributes = 
info->u.vesa_lfb.mode_attrs;
+
+               if (size >= offsetof(struct dom0_vga_console_info,
+                                    u.vesa_lfb.ext_lfb_base)
+                   + sizeof(info->u.vesa_lfb.ext_lfb_base)
+                   && info->u.vesa_lfb.ext_lfb_base) {
+                       screen_info->ext_lfb_base = 
info->u.vesa_lfb.ext_lfb_base;
+                       screen_info->capabilities |= 
VIDEO_CAPABILITY_64BIT_BASE;
+               }
                break;
        }
 }
--- a/include/xen/interface/xen.h
+++ b/include/xen/interface/xen.h
@@ -722,6 +722,9 @@ struct dom0_vga_console_info {
                        uint32_t gbl_caps;
                        /* Mode attributes (offset 0x0, VESA command 0x4f01). */
                        uint16_t mode_attrs;
+                       uint16_t pad;
+                       /* high 32 bits of lfb_base */
+                       uint32_t ext_lfb_base;
                } vesa_lfb;
        } u;
 };