[Xen-devel] {xen, dom0}_vga_console_info.u.vesa_lfb.lfb_base field too small

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Hi,

I have a machine that allocate vesa LFB above 4GB, as reported by UEFI
GOP. At 0x4000000000 to be specific.
vga_console_info.u.vesa_lfb.lfb_base is a 32bit field, so it gets
truncated, leading to all kind of memory corruptions when something
writes there.
If that would be only about Xen, that wouldn't be that bad, but
unfortunately exactly the same structure is used as an interface for
dom0 start info (at least PV one).
My only idea is to introduce yet another entry in *_vga_console_info.u
union (efi_lfb64?) with a 64bit lfb_base field. And mark it in
video_type (XEN_VGATYPE_EFI_LFB64?). But I'm not sure how non-patched
Linux (or other supported OSes) would respond to this. xen_init_vga() in
Linux doesn't seem to bail on unknown video_type, so it may be fragile.

Any better ideas?

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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